This test was assuming that /usr/include was in the system header search
path. That assumption should never have been true, but it was until
I fixed it. Now that its fixed, add a triple here to get correct
behavior even on Windows.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143863 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed