Revert "Revert "Merge to upstream r304942.""

This reverts commit 38a0d5af7e.

Test: make checkbuild
Test: ./run_tests.py
Test: ./run_tests.py --bitness 64

test/std/utilities/variant/variant.get/get_index.pass.cpp

@@ -10,6 +10,13 @@
 
 // UNSUPPORTED: c++98, c++03, c++11, c++14
 
+// XFAIL: with_system_cxx_lib=macosx10.12
+// XFAIL: with_system_cxx_lib=macosx10.11
+// XFAIL: with_system_cxx_lib=macosx10.10
+// XFAIL: with_system_cxx_lib=macosx10.9
+// XFAIL: with_system_cxx_lib=macosx10.7
+// XFAIL: with_system_cxx_lib=macosx10.8
+
 // <variant>
 
 // template <size_t I, class... Types>