Validate PowerShell prerequisite. Update documentation.

1 files changed, 10 insertions, 0 deletions

diff --git a/build.cmd b/build.cmd
index 5ace7f7d6d..f0c219b69f 100644
--- a/build.cmd
+++ b/build.cmd
@@ -212,6 +212,10 @@ if defined __MscorlibOnly goto CheckVS
 
 echo %__MsgPrefix%Checking prerequisites
 
+:: Validate that PowerShell is accessibile.
+for %%X in (powershell.exe) do (set __PSDir=%%~$PATH:X)
+if not defined __PSDir goto NoPS
+
 :: Eval the output from probe-win1.ps1
 for /f "delims=" %%a in ('powershell -NoProfile -ExecutionPolicy RemoteSigned "& ""%__SourceDir%\pal\tools\probe-win.ps1"""') do %%a
 
@@ -650,6 +654,12 @@ echo     build all x64 x86 Checked Release
 echo        -- builds x64 and x86 architectures, Checked and Release build types for each
 exit /b 1
 
+:NoPS
+echo PowerShell is a prerequisite to build this repository, but it is not accessible.
+echo Ensure that it is defined in the PATH environment variable.
+echo Typically it should be %%SYSTEMROOT%%\System32\WindowsPowerShell\v1.0\.
+exit /b 1
+
 :NoVS
 echo Visual Studio 2015+ ^(Community is free^) is a prerequisite to build this repository.
 echo See: https://github.com/dotnet/coreclr/blob/master/Documentation/project-docs/developer-guide.md#prerequisites