[DebugInfo] Follow-up bug fix on "Fixing a couple of DI duplication bugs of CloneModule"

Apparently, DebugInfoFinder::processCompileUnit doesn't process all
of the possible kinds of DIImportedEntit'ies, e.g. DIGlobalVariable's.

Previously introduced `llvm_unreachable` is therefore incorrect.
Removing it here.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330167 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed