Fixing powershell.exe lib paths and more thoroughly cleaning the powershell-native directory (#2758)

build.psm1

@@ -120,6 +120,11 @@ function Start-PSBuild {
         Push-Location $PSScriptRoot
         try {
             git clean -fdX
+            # Extra cleaning is required to delete the CMake temporary files. 
+            # These are not cleaned when using "X" and cause CMake to retain state, leading to
+            # mis-configured environment issues when switching between x86 and x64 compilation
+            # environments.
+            git clean -fdx .\src\powershell-native
         } finally {
             Pop-Location
         }

src/powershell-native/nativemsh/pwrshexe/CMakeLists.txt

@@ -20,16 +20,18 @@ if (BUILD_ONECORE)
     #
     # Configure lib directories so that CI picks up onecore.lib
     #
-    SET (WindowsSdkDir $ENV{WindowsSdkDir})
-    SET (WindowsSDKVersion $ENV{WindowsSDKVersion})
-    SET (WindowsSDKLibBase "${WindowsSdkDir}/Lib/${WindowsSDKVersion}")
-    SET (OneCoreLibBase "$ENV{VCInstallDir}lib/onecore/amd64")
+    if (BUILD_ARCH_AMD64)
+        SET (WindowsSdkDir $ENV{WindowsSdkDir})
+        SET (WindowsSDKVersion $ENV{WindowsSDKVersion})
+        SET (WindowsSDKLibBase "${WindowsSdkDir}/Lib/${WindowsSDKVersion}")
+        SET (OneCoreLibBase "$ENV{VCInstallDir}lib/onecore/amd64")
 
-    SET (LibraryPath)
-    list (APPEND LibraryPath "${OneCoreLibBase}")
-    list (APPEND LibraryPath "${WindowsSDKLibBase}ucrt/${WindowsSDKPlatform}")
-    list (APPEND LibraryPath "${WindowsSDKLibBase}um/${WindowsSDKPlatform}" )
-    link_directories(${LibraryPath})
+        SET (LibraryPath)
+        list (APPEND LibraryPath "${OneCoreLibBase}")
+        list (APPEND LibraryPath "${WindowsSDKLibBase}ucrt/${WindowsSDKPlatform}")
+        list (APPEND LibraryPath "${WindowsSDKLibBase}um/${WindowsSDKPlatform}" )
+        link_directories(${LibraryPath})
+    endif ()
 
 else ()
     # Settings to use when creating PowerShell.exe for Windows on full SKUs or downlevel platforms