[builtins] Build for arm64_32 for watchOS (Darwin)

Trying to build the builtins code fails because `arm64_32_SOURCES` is
missing. Setting it to the same list used for `aarch64_SOURCES` solves
that problem and allow the builtins to compile for that architecture.

Additionally, arm64_32 is added as a possible architecture for watchos
platforms.

Reviewed By: compnerd

Differential Revision: https://reviews.llvm.org/D99690

Author: drodriguez

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

@@ -122,7 +122,7 @@ if(APPLE)
     set(DARWIN_watchos_BUILTIN_MIN_VER 2.0)
     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)
+    set(DARWIN_watchos_BUILTIN_ALL_POSSIBLE_ARCHS armv7 armv7k arm64_32)
     set(DARWIN_watchossim_BUILTIN_ALL_POSSIBLE_ARCHS ${X86})
   endif()
   if(COMPILER_RT_ENABLE_TVOS)

compiler-rt/lib/builtins/CMakeLists.txt

@@ -555,6 +555,7 @@ set(armv7s_SOURCES ${arm_SOURCES})
 set(armv7k_SOURCES ${arm_SOURCES})
 set(arm64_SOURCES ${aarch64_SOURCES})
 set(arm64e_SOURCES ${aarch64_SOURCES})
+set(arm64_32_SOURCES ${aarch64_SOURCES})
 
 # macho_embedded archs
 set(armv6m_SOURCES ${thumb1_SOURCES})