And here is the official Patch from libcxx:
--- libcxx/trunk/include/__locale 2017/05/31 22:14:05 304360
+++ libcxx/trunk/include/__locale 2017/08/03 04:28:10 309920
@@ -34,7 +34,7 @@
# include <support/solaris/xlocale.h>
#elif defined(_NEWLIB_VERSION)
# include <support/newlib/xlocale.h>
-#elif (defined(__GLIBC__) || defined(__APPLE__) || defined(__FreeBSD__) \
+#elif (defined(__APPLE__) || defined(__FreeBSD__) \
|| defined(__EMSCRIPTEN__) || defined(__IBMCPP__))
# include <xlocale.h>
#elif defined(__Fuchsia__)
Refer to: Patch Source