Debug Info Verifier: enable verification of DICompileUnit.

Debug Info Verifier: enable verification of DICompileUnit.

We used to call Verify before adding DICompileUnit to the list, and now we
remove the check and always add DICompileUnit to the list in DebugInfoFinder,
so we can verify them later on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187237 91177308-0d34-0410-b5e6-96231b3b80d8