[libc++] Correct XFAILs for the C++20 Synchronization Library
Technically, these tests don't only fail against macosx10.9 to 10.15,
but really against any released macOS yet.
diff --git a/libcxx/test/std/thread/thread.latch/try_wait.pass.cpp b/libcxx/test/std/thread/thread.latch/try_wait.pass.cpp
index e06b80f..476ec8b 100644
--- a/libcxx/test/std/thread/thread.latch/try_wait.pass.cpp
+++ b/libcxx/test/std/thread/thread.latch/try_wait.pass.cpp
@@ -9,7 +9,9 @@
// UNSUPPORTED: libcpp-has-no-threads
// UNSUPPORTED: c++03, c++11
-// This test requires the dylib support introduced in D68480
+// This test requires the dylib support introduced in D68480,
+// which hasn't shipped yet.
+// XFAIL: with_system_cxx_lib=macosx
// XFAIL: with_system_cxx_lib=macosx10.15
// XFAIL: with_system_cxx_lib=macosx10.14
// XFAIL: with_system_cxx_lib=macosx10.13