Allow additional output since e.g. OSX appends flags like

"-mlinker-version=264.3.102" automatically. Wiring down a target on the
other hand is problematic as this actually needs to run codegen and
doesn't work with -###.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288827 91177308-0d34-0410-b5e6-96231b3b80d8