Fix strict aliasing violation from conditional typedef of wchar_t by building entire project as C++ for Unix (#6801)

Enable building CoreCLR as C++ project on Unix

This series of patches fixes the strict aliasing violation from
the conditional typedef of wchar_t in src/pal/inc/pal_char16.h:40

* rename c files to cpp
* modify all cmake files to change .c files to .cpp
* apply c++ linkage to templates

1 files changed, 4 insertions, 5 deletions

diff --git a/src/inc/CMakeLists.txt b/src/inc/CMakeLists.txt
index 803ca3bcc7..d38fa40773 100644
--- a/src/inc/CMakeLists.txt
+++ b/src/inc/CMakeLists.txt
@@ -50,23 +50,22 @@ add_compile_options(/TC)
 
 else()
 
-#The MIDL tool exists for Windows only, so for other systems, we have the prebuilt xxx_i.c files checked in
+#The MIDL tool exists for Windows only, so for other systems, we have the prebuilt xxx_i.cpp files checked in
 
 # The prebuilt files contain extra '!_MIDL_USE_GUIDDEF_' after the #endif, but not in the comment.
 # In order to not to have to modify these prebuilt files, we disable the extra tokens warning.
 add_compile_options(-Wno-extra-tokens)
-
+add_compile_options(-D_MIDL_USE_GUIDDEF_)
 foreach(IDL_SOURCE IN LISTS CORGUIDS_IDL_SOURCES)
    get_filename_component(IDLNAME ${IDL_SOURCE} NAME_WE)
-   set(C_SOURCE ../pal/prebuilt/idl/${IDLNAME}_i.c)
+   set(C_SOURCE ../pal/prebuilt/idl/${IDLNAME}_i.cpp)
    list(APPEND CORGUIDS_SOURCES ${C_SOURCE})
 endforeach(IDL_SOURCE)
 
 add_compile_options(-fPIC)
-
 endif(WIN32)
 
-# Compile *_i.c to lib
+# Compile *_i.cpp to lib
 _add_library(corguids ${CORGUIDS_SOURCES})
 
 # Binplace the inc files for packaging later.