[debuginfo-tests] Support moving debuginfo-tests to llvm/projects

Summary:
Add cmake and lit files needed to run these tests as an
external project.  Also, copy test_debuginfo.pl from llvm/utils since
it's only used here.  The copy in llvm/utils must be maintained as
long as bots continue to include debuginfo-tests in clang/test.

This patch depends on clang patch https://reviews.llvm.org/D41055.

Reviewers: zturner, aprantl

Reviewed By: aprantl

Subscribers: mgorny, llvm-commits, JDevlieghere

Differential Revision: https://reviews.llvm.org/D40971

llvm-svn: 320495