librhash: aligned_alloc is not available with IBM XLClang on Linux

The declaration exists in `<stdlib.h>` but the compiler warns about
its allocation alignment attribute.

Utilities/cmlibrhash/librhash/util.h

@@ -42,6 +42,7 @@ extern "C" {
 # define rhash_aligned_free(ptr) _aligned_free(ptr)
 
 #elif !defined(NO_STDC_ALIGNED_ALLOC) && (__STDC_VERSION__ >= 201112L || defined(_ISOC11_SOURCE)) \
+	&& !(defined(__ibmxl__) && defined(__clang__) && defined(__linux__)) \
 	&& !defined(__APPLE__) && !defined(__HAIKU__) && !defined(__sun) \
 	&& (!defined(__ANDROID_API__) || __ANDROID_API__ >= 28)