[builtins] Use __APPLE__ instead of __MACH__ in check
The latter doesn't seem to be working for all targets. This addresses
the issue introduced in r359413.
#if defined(__ELF__) || defined(__MINGW32__) || defined(__wasm__)
#define COMPILER_RT_ALIAS(name, aliasname) \
COMPILER_RT_ABI __typeof(name) aliasname __attribute__((__alias__(#name)));
-#elif defined(__MACH__)
+#elif defined(__APPLE__)
#define COMPILER_RT_ALIAS(name, aliasname) \
__asm__(".globl " SYMBOL_NAME(aliasname)); \
__asm__(SYMBOL_NAME(aliasname) " = " SYMBOL_NAME(name)); \
