Index: libcxx/src/filesystem/int128_builtins.cpp
===================================================================
--- libcxx/src/filesystem/int128_builtins.cpp
+++ libcxx/src/filesystem/int128_builtins.cpp
@@ -16,7 +16,12 @@
 #include "__config"
 #include "climits"
 
-#if !defined(_LIBCPP_HAS_NO_INT128)
+// Apple platforms provide compiler_rt, so there is no need to define __muloti4 here.
+#if !defined(__APPLE__)
+#  define _LIBCPP_DEFINE_MULOTI4_IN_DYLIB
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_INT128) && defined(_LIBCPP_DEFINE_MULOTI4_IN_DYLIB)
 
 extern "C" __attribute__((no_sanitize("undefined")))
 __int128_t __muloti4(__int128_t a, __int128_t b, int* overflow) {