[compiler-rt] [CMake] Skip find_darwin_sdk_dir on disabled platforms (llvm#163591)

find_darwin_sdk_dir can be slow, especially if xcrun does not
immediately find the corresponding SDK (i.e. because it is missing).

This skips those checks if the user has already set the corresponding
CMake variable to disable the platform anyway.

Author: ndrewh

compiler-rt/cmake/builtin-config-ix.cmake

@@ -117,14 +117,22 @@ include(CompilerRTDarwinUtils)
 if(APPLE)
 
   find_darwin_sdk_dir(DARWIN_osx_SYSROOT macosx)
-  find_darwin_sdk_dir(DARWIN_iossim_SYSROOT iphonesimulator)
-  find_darwin_sdk_dir(DARWIN_ios_SYSROOT iphoneos)
-  find_darwin_sdk_dir(DARWIN_watchossim_SYSROOT watchsimulator)
-  find_darwin_sdk_dir(DARWIN_watchos_SYSROOT watchos)
-  find_darwin_sdk_dir(DARWIN_tvossim_SYSROOT appletvsimulator)
-  find_darwin_sdk_dir(DARWIN_tvos_SYSROOT appletvos)
-  find_darwin_sdk_dir(DARWIN_xrossim_SYSROOT xrsimulator)
-  find_darwin_sdk_dir(DARWIN_xros_SYSROOT xros)
+  if(COMPILER_RT_ENABLE_IOS)
+    find_darwin_sdk_dir(DARWIN_iossim_SYSROOT iphonesimulator)
+    find_darwin_sdk_dir(DARWIN_ios_SYSROOT iphoneos)
+  endif()
+  if(COMPILER_RT_ENABLE_WATCHOS)
+    find_darwin_sdk_dir(DARWIN_watchossim_SYSROOT watchsimulator)
+    find_darwin_sdk_dir(DARWIN_watchos_SYSROOT watchos)
+  endif()
+  if(COMPILER_RT_ENABLE_TVOS)
+    find_darwin_sdk_dir(DARWIN_tvossim_SYSROOT appletvsimulator)
+    find_darwin_sdk_dir(DARWIN_tvos_SYSROOT appletvos)
+  endif()
+  if(COMPILER_RT_ENABLE_XROS)
+    find_darwin_sdk_dir(DARWIN_xrossim_SYSROOT xrsimulator)
+    find_darwin_sdk_dir(DARWIN_xros_SYSROOT xros)
+  endif()
 
   # Get supported architecture from SDKSettings.
   function(sdk_has_arch_support sdk_path os arch has_support)

compiler-rt/cmake/config-ix.cmake

@@ -408,12 +408,18 @@ if(APPLE)
   include(CompilerRTDarwinUtils)
 
   find_darwin_sdk_dir(DARWIN_osx_SYSROOT macosx)
-  find_darwin_sdk_dir(DARWIN_iossim_SYSROOT iphonesimulator)
-  find_darwin_sdk_dir(DARWIN_ios_SYSROOT iphoneos)
-  find_darwin_sdk_dir(DARWIN_watchossim_SYSROOT watchsimulator)
-  find_darwin_sdk_dir(DARWIN_watchos_SYSROOT watchos)
-  find_darwin_sdk_dir(DARWIN_tvossim_SYSROOT appletvsimulator)
-  find_darwin_sdk_dir(DARWIN_tvos_SYSROOT appletvos)
+  if(COMPILER_RT_ENABLE_IOS)
+    find_darwin_sdk_dir(DARWIN_iossim_SYSROOT iphonesimulator)
+    find_darwin_sdk_dir(DARWIN_ios_SYSROOT iphoneos)
+  endif()
+  if(COMPILER_RT_ENABLE_WATCHOS)
+    find_darwin_sdk_dir(DARWIN_watchossim_SYSROOT watchsimulator)
+    find_darwin_sdk_dir(DARWIN_watchos_SYSROOT watchos)
+  endif()
+  if(COMPILER_RT_ENABLE_TVOS)
+    find_darwin_sdk_dir(DARWIN_tvossim_SYSROOT appletvsimulator)
+    find_darwin_sdk_dir(DARWIN_tvos_SYSROOT appletvos)
+  endif()
 
   if(NOT DARWIN_osx_SYSROOT)
     message(WARNING "Could not determine OS X sysroot, trying /usr/include")