later, '-L <dir>' is allowed, but rewrite these in the driver as '-L<dir>' to
maintain backward compatibility.  The same is true for the -I option.
rdar://12366753

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167054 91177308-0d34-0410-b5e6-96231b3b80d8