Don't pass %s twice to clang -cc1.

The reason this clang invocation was failing is that it had two %s. We would
close stdout after the first one and report a fatal error when trying to
print the second.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@187122 91177308-0d34-0410-b5e6-96231b3b80d8