Revert r158423 corresponding to r158796, "test/Driver/warning-options.cpp: Mark as XFAIL:cygming. -pedantic is passed with gcc-as driver. PR12920"

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158915 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Driver/warning-options.cpp b/test/Driver/warning-options.cpp
index f40121f..ce434ab 100644
--- a/test/Driver/warning-options.cpp
+++ b/test/Driver/warning-options.cpp
@@ -8,7 +8,3 @@
 // CHECK: unknown warning option '-Wmonkey'
 // CHECK: unknown warning option '-Wno-monkey'
 // CHECK: unknown warning option '-Wno-unused-command-line-arguments'; did you mean '-Wno-unused-command-line-argument'?
-
-// PR12920: They use gcc driver. Clang tends to pass -pedantic to gcc-as and gcc-ld.
-// XFAIL: cygwin,mingw32
-