--- a/buildtools/third_party/libc++/__config_site
+++ b/buildtools/third_party/libc++/__config_site
@@ -49,3 +49,4 @@
 #define _LIBCPP_REMOVE_TRANSITIVE_INCLUDES
 
+#define  _LIBCPP_HAS_MUSL_LIBC
 #endif // _LIBCPP_CONFIG_SITE