Target/X86/MCTargetDesc/X86MCAsmInfo.cpp: Enable DwarfCFI (aka DW2) on Cygming.

Cygwin-1.7 supports dw2. Some recent mingw distros support one, too.
I have confirmed test-suite/SingleSource/Benchmarks/Shootout-C++/except.cpp can pass on Cygwin.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154247 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed