MDEV-36995: ifunc is not supported by musl

Only glibc and not musl currently supports the mechanisms of IFUNC.
This fixes 11.8 branch build on Alpine Linux.

Build error was:
mariadb-11.8.2/sql/vector_mhnsw.cc: In static member function 'static const FVector* FVector::create(metric_type, void*, const void*, size_t)':
mariadb-11.8.2/sql/vector_mhnsw.cc:299:19: error: multiversioning needs 'ifunc' which is not supported on this target
  299 |   static FVector *align_ptr(void *ptr) { return (FVector*)ptr; }
      |                   ^~~~~~~~~
mariadb-11.8.2/sql/vector_mhnsw.cc:113:3: error: use of multiversioned function without a default

Author: fauust

sql/bloom_filters.h

@@ -35,7 +35,7 @@ SOFTWARE.
   implementation for now.
 */
 #define DEFAULT_IMPLEMENTATION
-#if __GNUC__ > 7
+#if __GNUC__ > 7 && defined(__GLIBC__)
 #ifdef __x86_64__
 #ifdef HAVE_IMMINTRIN_H
 #include <immintrin.h>