[compiler-rt][Darwin] Add arm64 to simulator platforms

I was looking around and noticed that builtins for iossim, tvossim
and watchossim was missing arm64 builds, while apple's clang
toolchain ship with these. After a bit of searching around it just
seems like these are not listed correctly in CMake to be enabled.

I enabled just arm64 since I saw that Apple clang didn't include
arm64e.

Reviewed By: t.p.northover

Differential Revision: https://reviews.llvm.org/D118759

(cherry picked from commit a8e5ce7)

Author: Tobias Hieta

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

@@ -115,7 +115,7 @@ if(APPLE)
     set(DARWIN_ios_BUILTIN_MIN_VER_FLAG
       ${DARWIN_ios_MIN_VER_FLAG}=${DARWIN_ios_BUILTIN_MIN_VER})
     set(DARWIN_ios_BUILTIN_ALL_POSSIBLE_ARCHS ${ARM64} ${ARM32})
-    set(DARWIN_iossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86} ${X86_64})
+    set(DARWIN_iossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86} ${X86_64} arm64)
   endif()
   if(COMPILER_RT_ENABLE_WATCHOS)
     list(APPEND DARWIN_EMBEDDED_PLATFORMS watchos)
@@ -124,7 +124,7 @@ if(APPLE)
     set(DARWIN_watchos_BUILTIN_MIN_VER_FLAG
       ${DARWIN_watchos_MIN_VER_FLAG}=${DARWIN_watchos_BUILTIN_MIN_VER})
     set(DARWIN_watchos_BUILTIN_ALL_POSSIBLE_ARCHS armv7 armv7k arm64_32)
-    set(DARWIN_watchossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86})
+    set(DARWIN_watchossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86} arm64)
   endif()
   if(COMPILER_RT_ENABLE_TVOS)
     list(APPEND DARWIN_EMBEDDED_PLATFORMS tvos)
@@ -133,7 +133,7 @@ if(APPLE)
     set(DARWIN_tvos_BUILTIN_MIN_VER_FLAG
       ${DARWIN_tvos_MIN_VER_FLAG}=${DARWIN_tvos_BUILTIN_MIN_VER})
     set(DARWIN_tvos_BUILTIN_ALL_POSSIBLE_ARCHS armv7 arm64)
-    set(DARWIN_tvossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86} ${X86_64})
+    set(DARWIN_tvossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86} ${X86_64} arm64)
   endif()
 
   set(BUILTIN_SUPPORTED_OS osx)