[driver] The failure of any phase (e.g., preprocess, compile, assemble) for a
single translation unit should prevent later phases from executing.  Otherwise,
this generates lots of noise in build systems.  This a fallout from r173825.
Patch by Matthew Curtis <mcurtis@codeaurora.org>.
rdar://13298009

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176198 91177308-0d34-0410-b5e6-96231b3b80d8