--- ./buildtools/third_party/libc++/__config_site.orig
+++ ./buildtools/third_party/libc++/__config_site
@@ -18,7 +18,7 @@
 /* #undef _LIBCPP_ABI_FORCE_MICROSOFT */
 /* #undef _LIBCPP_HAS_NO_THREADS */
 /* #undef _LIBCPP_HAS_NO_MONOTONIC_CLOCK */
-/* #undef _LIBCPP_HAS_MUSL_LIBC */
+#define _LIBCPP_HAS_MUSL_LIBC 1
 /* #undef _LIBCPP_HAS_THREAD_API_PTHREAD */
 /* #undef _LIBCPP_HAS_THREAD_API_EXTERNAL */
 /* #undef _LIBCPP_HAS_THREAD_API_WIN32 */