Conditionalise the addition of Aarch64 function Multi versioning support on aarch64 target (llvm#143749)

Currently, `ENABLE_BAREMETAL_AARCH64_FMV` is added to builtin defines
for all baremetal targets though it is only needed for aarch64. This
patch fixes this by adding it only for aarch64 target.

Author: Garvit Gupta

compiler-rt/lib/builtins/CMakeLists.txt

@@ -884,7 +884,11 @@ else ()
   if(COMPILER_RT_DISABLE_AARCH64_FMV)
     list(APPEND BUILTIN_DEFS DISABLE_AARCH64_FMV)
   elseif(COMPILER_RT_BAREMETAL_BUILD)
-    list(APPEND BUILTIN_DEFS ENABLE_BAREMETAL_AARCH64_FMV)
+    foreach (arch ${BUILTIN_SUPPORTED_ARCH})
+      if("${arch}" MATCHES "arm64|aarch64")
+        list(APPEND BUILTIN_DEFS ENABLE_BAREMETAL_AARCH64_FMV)
+      endif()
+    endforeach ()
   endif()
 
   append_list_if(COMPILER_RT_HAS_ASM_LSE HAS_ASM_LSE BUILTIN_DEFS)