builtins: replicate aarch64.c change into aarch64.h

Perform the same macro expansion in the header to improve handling
the various ARM64 environments which use different CPU architecture
identification macro spellings.

compiler-rt/lib/builtins/cpu_model/aarch64.h

@@ -8,7 +8,7 @@
 
 #include "cpu_model.h"
 
-#if !defined(__aarch64__)
+#if !defined(__aarch64__) && !defined(__arm64__) && !defined(_M_ARM64)
 #error This file is intended only for aarch64-based targets
 #endif