[libcxx] Mark test cxa_deleted_virtual.pass.cpp as failing for previous libcxx versions.

[vsapsai]

Summary

r313500 added a fix for undefined "___cxa_deleted_virtual" symbol.
Previous libcxx versions don't have the fix and corresponding test
should be failing.

rdar://problem/34521053

[ahatanak]

LGTM

libcxx/trunk/test/libcxx/language.support/cxa_deleted_virtual.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++98, c++03
 
 // Test exporting the symbol: "__cxa_deleted_virtual" in macosx
+// But don't expect the symbol to be exported in previous versions.
+//
+// XFAIL: with_system_cxx_lib=macosx10.13
+// 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=macosx10.8
+// XFAIL: with_system_cxx_lib=macosx10.7
 
 struct S { virtual void f() = delete; virtual ~S() {} };
 int main() {
   S *s = new S;
   delete s;
 }