define cblas_xerbla_64 as a weak symbol

Author: mkrainiuk

CBLAS/include/cblas_64.h

@@ -572,7 +572,11 @@ void cblas_zher2k_64(CBLAS_LAYOUT layout, CBLAS_UPLO Uplo,
                   const void *B, const int64_t ldb, const double beta,
                   void *C, const int64_t ldc);
 
-void cblas_xerbla_64(int64_t p, const char *rout, const char *form, ...);
+void
+#ifdef HAS_ATTRIBUTE_WEAK_SUPPORT
+__attribute__((weak))
+#endif
+cblas_xerbla_64(int64_t p, const char *rout, const char *form, ...);
 
 #ifdef __cplusplus
 }