[compiler-rt] Adds builtins support for xros. (#83484)

Adds support for xros when compiling builtins. This is disabled by
default and controlled with COMPILER_RT_ENABLE_XROS, similar to
watchOS/tvOS.

Author: rohit-rao

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

@@ -156,6 +156,7 @@ if(APPLE)
 
   option(COMPILER_RT_ENABLE_WATCHOS "Enable building for watchOS - Experimental" Off)
   option(COMPILER_RT_ENABLE_TVOS "Enable building for tvOS - Experimental" Off)
+  option(COMPILER_RT_ENABLE_XROS "Enable building for xrOS - Experimental" Off)
 
 else()
   option(COMPILER_RT_DEFAULT_TARGET_ONLY "Build builtins only for the default target" Off)

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

@@ -92,6 +92,8 @@ if(APPLE)
   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)
 
   # Get supported architecture from SDKSettings.
   function(sdk_has_arch_support sdk_path os arch has_support)
@@ -162,6 +164,11 @@ if(APPLE)
       list(APPEND DARWIN_tvossim_BUILTIN_ALL_POSSIBLE_ARCHS arm64)
     endif()
   endif()
+  if(COMPILER_RT_ENABLE_XROS)
+    list(APPEND DARWIN_EMBEDDED_PLATFORMS xros)
+    set(DARWIN_xros_BUILTIN_ALL_POSSIBLE_ARCHS ${ARM64} ${ARM32})
+    set(DARWIN_xrossim_BUILTIN_ALL_POSSIBLE_ARCHS arm64)
+  endif()
 
   set(BUILTIN_SUPPORTED_OS osx)