Cache VCVARS variables for incremental building on Windows

The initial configure & generate of a build on Windows should have
the necessary VCVARS set in the environment. After that, we should be
incrementally building with those same vars to avoid conflicts between
Windows SDKs.

Cache these vars so that the same Windows SDKs are consistently used
in future incremental builds.

Author: lanza

cmake/modules/SwiftConfigureSDK.cmake

@@ -12,9 +12,9 @@ include(SwiftAndroidSupport)
 function(_report_sdk prefix)
   message(STATUS "${SWIFT_SDK_${prefix}_NAME} SDK:")
   if("${prefix}" STREQUAL "WINDOWS")
-    message(STATUS "  UCRT Version: $ENV{UCRTVersion}")
-    message(STATUS "  UCRT SDK Dir: $ENV{UniversalCRTSdkDir}")
-    message(STATUS "  VC Dir: $ENV{VCToolsInstallDir}")
+    message(STATUS "  UCRT Version: ${UCRTVersion}")
+    message(STATUS "  UCRT SDK Dir: ${UniversalCRTSdkDir}")
+    message(STATUS "  VC Dir: ${VCToolsInstallDir}")
     if("${CMAKE_BUILD_TYPE}" STREQUAL "DEBUG")
       message(STATUS "  ${CMAKE_BUILD_TYPE} VC++ CRT: MDd")
     else()
@@ -250,6 +250,8 @@ macro(configure_sdk_windows name environment architectures)
   # Note: this has to be implemented as a macro because it sets global
   # variables.
 
+  swift_windows_cache_VCVARS()
+
   string(TOUPPER ${name} prefix)
   string(TOLOWER ${name} platform)
 
@@ -274,10 +276,10 @@ macro(configure_sdk_windows name environment architectures)
     # NOTE(compnerd) workaround incorrectly extensioned import libraries from
     # the Windows SDK on case sensitive file systems.
     swift_windows_arch_spelling(${arch} WinSDKArchitecture)
-    set(WinSDK${arch}UMDir "$ENV{UniversalCRTSdkDir}/Lib/$ENV{UCRTVersion}/um/${WinSDKArchitecture}")
+    set(WinSDK${arch}UMDir "${UniversalCRTSdkDir}/Lib/${UCRTVersion}/um/${WinSDKArchitecture}")
     set(OverlayDirectory "${CMAKE_BINARY_DIR}/winsdk_lib_${arch}_symlinks")
 
-    if(NOT EXISTS "$ENV{UniversalCRTSdkDir}/Include/$ENV{UCRTVersion}/um/WINDOWS.H")
+    if(NOT EXISTS "${UniversalCRTSdkDir}/Include/${UCRTVersion}/um/WINDOWS.H")
       file(MAKE_DIRECTORY ${OverlayDirectory})
 
       file(GLOB libraries RELATIVE "${WinSDK${arch}UMDir}" "${WinSDK${arch}UMDir}/*")

cmake/modules/SwiftWindowsSupport.cmake

@@ -15,65 +15,44 @@ function(swift_windows_arch_spelling arch var)
   endif()
 endfunction()
 
-function(swift_verify_windows_environment_variables)
-  set(VCToolsInstallDir $ENV{VCToolsInstallDir})
-  set(UniversalCRTSdkDir $ENV{UniversalCRTSdkDir})
-  set(UCRTVersion $ENV{UCRTVersion})
-
-  precondition(VCToolsInstallDir
-               MESSAGE
-                 "VCToolsInstallDir environment variable must be set")
-  precondition(UniversalCRTSdkDir
-               MESSAGE
-                 "UniversalCRTSdkDir environment variable must be set")
-  precondition(UCRTVersion
-               MESSAGE
-                 "UCRTVersion environment variable must be set")
-endfunction()
-
 function(swift_windows_include_for_arch arch var)
-  swift_verify_windows_environment_variables()
-
   set(paths
-        "$ENV{VCToolsInstallDir}/include"
-        "$ENV{UniversalCRTSdkDir}/Include/$ENV{UCRTVersion}/ucrt"
-        "$ENV{UniversalCRTSdkDir}/Include/$ENV{UCRTVersion}/shared"
-        "$ENV{UniversalCRTSdkDir}/Include/$ENV{UCRTVersion}/um")
+      "${VCToolsInstallDir}/include"
+      "${UniversalCRTSdkDir}/Include/${UCRTVersion}/ucrt"
+      "${UniversalCRTSdkDir}/Include/${UCRTVersion}/shared"
+      "${UniversalCRTSdkDir}/Include/${UCRTVersion}/um")
   set(${var} ${paths} PARENT_SCOPE)
 endfunction()
 
 function(swift_windows_lib_for_arch arch var)
-  swift_verify_windows_environment_variables()
   swift_windows_arch_spelling(${arch} ARCH)
 
   set(paths)
 
   # NOTE(compnerd) provide compatibility with VS2015 which had the libraries in
   # a directory called "Lib" rather than VS2017 which normalizes the layout and
   # places them in a directory named "lib".
-  if(IS_DIRECTORY "$ENV{VCToolsInstallDir}/Lib")
+  if(IS_DIRECTORY "${VCToolsInstallDir}/Lib")
     if(${ARCH} STREQUAL x86)
-      list(APPEND paths "$ENV{VCToolsInstallDir}/Lib/")
+      list(APPEND paths "${VCToolsInstallDir}/Lib/")
     else()
-      list(APPEND paths "$ENV{VCToolsInstallDir}/Lib/${ARCH}")
+      list(APPEND paths "${VCToolsInstallDir}/Lib/${ARCH}")
     endif()
   else()
-    list(APPEND paths "$ENV{VCToolsInstallDir}/lib/${ARCH}")
+    list(APPEND paths "${VCToolsInstallDir}/lib/${ARCH}")
   endif()
 
   list(APPEND paths
-          "$ENV{UniversalCRTSdkDir}/Lib/$ENV{UCRTVersion}/ucrt/${ARCH}"
-          "$ENV{UniversalCRTSdkDir}/Lib/$ENV{UCRTVersion}/um/${ARCH}")
+          "${UniversalCRTSdkDir}/Lib/${UCRTVersion}/ucrt/${ARCH}"
+          "${UniversalCRTSdkDir}/Lib/${UCRTVersion}/um/${ARCH}")
 
   set(${var} ${paths} PARENT_SCOPE)
 endfunction()
 
 function(swift_windows_generate_sdk_vfs_overlay flags)
-  swift_verify_windows_environment_variables()
-
-  get_filename_component(VCToolsInstallDir $ENV{VCToolsInstallDir} ABSOLUTE)
-  get_filename_component(UniversalCRTSdkDir $ENV{UniversalCRTSdkDir} ABSOLUTE)
-  set(UCRTVersion $ENV{UCRTVersion})
+  get_filename_component(VCToolsInstallDir ${VCToolsInstallDir} ABSOLUTE)
+  get_filename_component(UniversalCRTSdkDir ${UniversalCRTSdkDir} ABSOLUTE)
+  set(UCRTVersion ${UCRTVersion})
 
   # TODO(compnerd) use a target to avoid re-creating this file all the time
   configure_file("${SWIFT_SOURCE_DIR}/utils/WindowsSDKVFSOverlay.yaml.in"
@@ -85,3 +64,19 @@ function(swift_windows_generate_sdk_vfs_overlay flags)
       PARENT_SCOPE)
 endfunction()
 
+function(swift_verify_windows_VCVAR var)
+  if (NOT DEFINED "${var}" AND NOT DEFINED "ENV{${var}}")
+    message(FATAL_ERROR "${var} environment variable must be set")
+  endif()
+endfunction()
+
+function(swift_windows_cache_VCVARS)
+  swift_verify_windows_VCVAR(VCToolsInstallDir)
+  swift_verify_windows_VCVAR(UniversalCRTSdkDir)
+  swift_verify_windows_VCVAR(UCRTVersion)
+
+  set(VCToolsInstallDir $ENV{VCToolsInstallDir} CACHE STRING "")
+  set(UniversalCRTSdkDir $ENV{UniversalCRTSdkDir} CACHE STRING "")
+  set(UCRTVersion $ENV{UCRTVersion} CACHE STRING "")
+endfunction()
+