StdLib/LibC ARM AARCH64: do not redefine compiler intrinsics

The memset() function is a compiler intrinsic on AARCH64 and ARM, and
so is memmove() on ARM. Usually, redefining them as LibC currently does
is not a problem since only one version will be selected at link time
from the various static libraries that provide implementations. However,
under LTO, this is slightly different, since explicit references (in the
C code) and implicit references (emitted by the compiler backend) may
resolve to different versions (LTO vs non-LTO), causing conflicts.

So simply omit them for ARM/AARCH64 resp. ARM.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

StdLib/LibC/String/Misc.c

@@ -26,6 +26,7 @@
 
 extern char *sys_errlist[];
 
+#if !((defined(MDE_CPU_ARM) || defined(MDE_CPU_AARCH64)) && defined(__GNUC__))
 /** The memset function copies the value of c (converted to an unsigned char)
     into each of the first n characters of the object pointed to by s.
 
@@ -36,6 +37,7 @@ memset(void *s, int c, size_t n)
 {
   return SetMem( s, (UINTN)n, (UINT8)c);
 }
+#endif
 
 int
 strerror_r(int errnum, char *buf, size_t buflen)