Revert "Partially revert r214761 that asserted that all concrete debug info variables had DIEs, due to a failure on Darwin."

I believe this was addressed by r215157 and r215227, so let's have
another go at the bots, etc.

This reverts commit r214880.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215412 91177308-0d34-0410-b5e6-96231b3b80d8