More PAL layer cleanup for GNU and add build script support for GCC (#22369)

* Declare throw only when compiling for c++

Prevent the definition from getting defined multiple times and
map it to throw() only when compiling c++ code.

* Suppress warnings for tests

Suppress:
 -Wno-write-strings
 -Wno-sign-compare
 -Wno-narrowing
 -fpermissive
 -Wno-int-to-pointer-cast

to allow tests to compile

* Add gcc option to build.sh script

Following clangx.y model add -gccx.y command line
arguments with gcc5 and gcc7 being the currnetly supported
options.

* Allow environment variable to be used for TOOLCHAIN

Remove CLANG specific compiler options as well.

* Hide non-GNU compiler options

* Do not include local directory if cross compiling

[  0%] Building CXX object src/pal/src/eventprovider/tracepointprovider/CMakeFiles/coreclrtraceptprovider.dir/__/lttng/traceptprovdotnetruntime.cpp.o
cc1plus: error: include location "/usr/local/include" is unsafe for cross-compilation [-Werror=poison-system-directories]

* Suppress unknown pragma warnings

src/pal/src/exception/seh-unwind.cpp:37:0:
warning: ignoring #pragma clang diagnostic [-Wunknown-pragmas]
    #pragma clang diagnostic pop

Removing these cause compilation error on clang7 and arm as follows:

In file included from /bin/obj/Linux.arm.Debug/src/pal/src/libunwind/include/libunwind.h:9:
/src/pal/src/libunwind/include/libunwind-arm.h:247:9: error: empty struct has size 0 in C, size 1 in C++ [-Werror,-Wextern-c-compat]
typedef struct unw_tdep_save_loc
        ^
/src/pal/src/libunwind/include/libunwind-arm.h:288:9: error: empty struct has size 0 in C, size 1 in C++ [-Werror,-Wextern-c-compat]
typedef struct

* plt not useful for GNU and ARM64/ARM

src/pal/src/arch/arm64/callsignalhandlerwrapper.S: Assembler messages:
src/pal/src/arch/arm64/callsignalhandlerwrapper.S:31: Error: unexpected characters following instruction at operand 1 -- `bl signal_handler_worker@plt'
src/pal/src/arch/arm64/callsignalhandlerwrapper.S:32: Error: unexpected characters following instruction at operand 1 -- `bl signal_handler_worker@plt'

* Remove double const from argv in PAL_Initialize

Seeing compilation error with GNU for C source files as follows:

if (PAL_Initialize(argc, argv) != 0)
                          ^
src/pal/tests/palsuite/common/palsuite.h:21:0,
from src/pal/tests/palsuite/c_runtime/asinhf/test1/test1.c:18:
src/pal/inc/pal.h:374:1: note: expected ‘const char * const*’ but argument is of type ‘char **’

* Suppress format warnings using GNU for libunwind

warning: format ‘%li’ expects argument of type ‘long int’, but argument 3 has type ‘int’ [-Wformat=]
     Debug (4, " aligned frame, offset %li\n", f->cfa_reg_offset);

* Fix -fpermissive warnings for GNU

* Suppress unused variable warning in libunwind

src/pal/src/libunwind/include/libunwind-aarch64.h:201:5: warning: right-hand operand of comma expression has no effect [-Wunused-value]
 #define unw_tdep_getcontext(uc) (({     \
                                 ~~~~~~~~~
   unw_tdep_context_t *unw_ctx = (uc);     \
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   register uint64_t *unw_base asm ("x0") = (uint64_t*) unw_ctx->uc_mcontext.regs;  \
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   __asm__ __volatile__ (      \
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x0, x1, [%[base], #0]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x2, x3, [%[base], #16]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x4, x5, [%[base], #32]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x6, x7, [%[base], #48]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x8, x9, [%[base], #64]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x10, x11, [%[base], #80]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x12, x13, [%[base], #96]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x14, x13, [%[base], #112]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x16, x17, [%[base], #128]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x18, x19, [%[base], #144]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x20, x21, [%[base], #160]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x22, x23, [%[base], #176]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x24, x25, [%[base], #192]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x26, x27, [%[base], #208]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "stp x28, x29, [%[base], #224]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "str x30, [%[base], #240]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      "mov x1, sp\n" \
      ~~~~~~~~~~~~~~~~
      "stp x1, x30, [%[base], #248]\n" \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      : [base] "+r" (unw_base) : : "x1", "memory"); \
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   }), 0)

* Fix warning: ‘memset’ used with length equal to number of elements warning

Fix similar warnings to these by including the element size into total size
calculation.

src/pal/tests/palsuite/miscellaneous/SetEnvironmentVariableW/test1/test.cpp: In function ‘int main(int, char**)’:
src/pal/tests/palsuite/miscellaneous/SetEnvironmentVariableW/test1/test.cpp:89:31: warning: ‘memset’ used with length equal to number of elements without multiplication by element size [-Wmemset-elt-size]
     memset(NewValue,0,BUF_SIZE);

* Define CLR specific compiler option CLR_CMAKE_COMPILER

By the time toolchain.cmake is called, the compiler detection from
cmake is not active. We need an intermediate definition to pass
to compiler detection.

6 files changed, 29 insertions, 8 deletions

diff --git a/src/pal/src/CMakeLists.txt b/src/pal/src/CMakeLists.txt
index 8e69ee9ee9..be5b5bd872 100644
--- a/src/pal/src/CMakeLists.txt
+++ b/src/pal/src/CMakeLists.txt
@@ -5,7 +5,9 @@ if(CMAKE_SYSTEM_NAME STREQUAL Darwin OR CMAKE_SYSTEM_NAME STREQUAL FreeBSD)
   set(CLR_CMAKE_USE_SYSTEM_LIBUNWIND 1)
 endif(CMAKE_SYSTEM_NAME STREQUAL Darwin OR CMAKE_SYSTEM_NAME STREQUAL FreeBSD)
 
-include_directories(SYSTEM /usr/local/include)
+if(NOT DEFINED ENV{ROOTFS_DIR})
+  include_directories(SYSTEM /usr/local/include)
+endif()
 
 add_compile_options(-fPIC)
 
diff --git a/src/pal/src/examples/example1.cpp b/src/pal/src/examples/example1.cpp
index 576e76632e..fce8c367b5 100644
--- a/src/pal/src/examples/example1.cpp
+++ b/src/pal/src/examples/example1.cpp
@@ -32,7 +32,7 @@ int main(int argc, char *argv[])
   HANDLE h;
   unsigned int b;
 
-  PAL_Initialize(argc, (const char**)argv);
+  PAL_Initialize(argc, argv);
   SetCurrentDirectoryW(dir);
   SetCurrentDirectoryW(dir);
   h =  CreateFileW(src, GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_NEW, 0, NULL);
diff --git a/src/pal/src/exception/remote-unwind.cpp b/src/pal/src/exception/remote-unwind.cpp
index 4934e77115..fe7a4c814f 100644
--- a/src/pal/src/exception/remote-unwind.cpp
+++ b/src/pal/src/exception/remote-unwind.cpp
@@ -51,10 +51,14 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 // Sub-headers included from the libunwind.h contain an empty struct
 // and clang issues a warning. Until the libunwind is fixed, disable
 // the warning.
+#ifdef __llvm__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wextern-c-compat"
+#endif
 #include <libunwind.h>
+#ifdef __llvm__
 #pragma clang diagnostic pop
+#endif
 
 SET_DEFAULT_DEBUG_CHANNEL(EXCEPT);
 
diff --git a/src/pal/src/exception/seh-unwind.cpp b/src/pal/src/exception/seh-unwind.cpp
index 094036189c..3f40057d88 100644
--- a/src/pal/src/exception/seh-unwind.cpp
+++ b/src/pal/src/exception/seh-unwind.cpp
@@ -31,10 +31,14 @@ Abstract:
 // Sub-headers included from the libunwind.h contain an empty struct
 // and clang issues a warning. Until the libunwind is fixed, disable
 // the warning.
+#ifdef __llvm__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wextern-c-compat"
+#endif
 #include <libunwind.h>
+#ifdef __llvm__
 #pragma clang diagnostic pop
+#endif
 
 //----------------------------------------------------------------------
 // Virtual Unwinding
diff --git a/src/pal/src/init/pal.cpp b/src/pal/src/init/pal.cpp
index d683ca7345..f6bbd6a82c 100644
--- a/src/pal/src/init/pal.cpp
+++ b/src/pal/src/init/pal.cpp
@@ -153,7 +153,7 @@ int
 PALAPI
 PAL_Initialize(
     int argc,
-    const char *const argv[])
+    char *const argv[])
 {
     return Initialize(argc, argv, PAL_INITIALIZE);
 }
diff --git a/src/pal/src/libunwind/src/CMakeLists.txt b/src/pal/src/libunwind/src/CMakeLists.txt
index c035f64c11..98d3d3e7a9 100644
--- a/src/pal/src/libunwind/src/CMakeLists.txt
+++ b/src/pal/src/libunwind/src/CMakeLists.txt
@@ -7,6 +7,11 @@ set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
 include(configure.cmake)
 
+if (NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  add_compile_options(-Wformat=0)
+  add_compile_options(-Wno-unused-value)
+endif()
+
 # The HAVE___THREAD set to 1 causes creation of thread local variable with tls_model("initial-exec")
 # which is incompatible with usage of the unwind code in a shared library.
 add_definitions(-DHAVE___THREAD=0)
@@ -19,15 +24,19 @@ add_definitions(-D_GNU_SOURCE)
 # Ensure that the remote and local unwind code can reside in the same binary without name clashing
 add_definitions("-Ddwarf_search_unwind_table_int=UNW_OBJ(dwarf_search_unwind_table_int)")
 
-add_compile_options(-Wno-header-guard)
+if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  add_compile_options(-Wno-header-guard)
+endif()
 
 if(CLR_CMAKE_PLATFORM_ARCH_ARM)
     # Ensure that the remote and local unwind code can reside in the same binary without name clashing
     add_definitions("-Darm_search_unwind_table=UNW_OBJ(arm_search_unwind_table)")
     # Disable warning in asm: use of SP or PC in the list is deprecated
     add_compile_options(-Wno-inline-asm)
-    # Disable warning due to labs function called on unsigned argument
-    add_compile_options(-Wno-absolute-value)
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+        # Disable warning due to labs function called on unsigned argument
+        add_compile_options(-Wno-absolute-value)
+    endif()
     # Disable warning due to incorrect format specifier in debugging printf via the Debug macro
     add_compile_options(-Wno-format)
     # Disable warning for a bug in the libunwind source src/arm/Gtrace.c:529, but not in code that we exercise
@@ -41,8 +50,10 @@ if(CLR_CMAKE_PLATFORM_ARCH_ARM)
     # the include/tdep-arm to include directories
     include_directories(../include/tdep-arm)
 elseif(CLR_CMAKE_PLATFORM_ARCH_ARM64)
-    # Disable warning due to labs function called on unsigned argument
-    add_compile_options(-Wno-absolute-value)
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+        # Disable warning due to labs function called on unsigned argument
+        add_compile_options(-Wno-absolute-value)
+    endif()
     # We compile code with -std=c99 and the asm keyword is not recognized as it is a gnu extension
     add_definitions(-Dasm=__asm__)
 elseif(CLR_CMAKE_PLATFORM_ARCH_I386)