[Debugify] Print the output to stderr

Currently debugify prints it's output to stdout,
with this patch all the output generated goes to stderr.

This change lets us use debugify without taking away
the ability to pipe the output to other llvm tools.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332642 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed