ASTMatchersTests/matchesConditionallyWithCuda: Add -fno-ms-extensions, and get rid of initializer list.

I am not sure whether -xcuda might imply -fno-ms-extensions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214876 91177308-0d34-0410-b5e6-96231b3b80d8