Apparently XFAIL tests that are supposed to fail to compile can be problematic. They still get compiled, and if the compile succeeds, the buildbots complain. Replace the XFAIL with #error.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@267591 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/re/re.alg/re.alg.match/basic.fail.cpp

@@ -18,12 +18,14 @@
 //                    regex_constants::match_flag_type = 
 //                      regex_constants::match_default) = delete;
 
-// XFAIL: C++98, c++03, c++11
-
 #include <regex>
 #include <cassert>
 #include "test_macros.h"
 
+#if TEST_STD_VER < 14
+#error
+#endif
+
 int main()
 {
     {