Since the last import from upstream libsanitizer, the output has changed
and now looks more like this:

READ of size 6 at 0x7ff7beb2a144 thread T0
    #0 0x101cf7796 in MemcmpInterceptorCommon(void*, int (*)(void const*, void const*, unsigned long), void const*, void const*, unsigned long) sanitizer_common_interceptors.inc:813
    #1 0x101cf7b99 in memcmp sanitizer_common_interceptors.inc:840
    #2 0x108a0c39f in __stack_chk_guard+0xf (dyld:x86_64+0x8039f)

so let's adjust the pattern accordingly.

gcc/testsuite/ChangeLog:

	* c-c++-common/asan/memcmp-1.c: Adjust pattern on darwin.