Driver: Move crash report command mangling into Command::Print

This pushes the logic for generating a crash reproduction script
entirely into Command::Print, instead of Command doing half of the
work and then relying on textual substitution for the rest. This makes
this logic much easier to read and will simplify fixing a couple of
issues in this area.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@220305 91177308-0d34-0410-b5e6-96231b3b80d8