[PR18809] Revert r201187, "DebugInfo: Don't include the name of the CU file in the line table file list when it's unneeded"

It really crashes cygwin's stage2 configure with "clang -g".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201351 91177308-0d34-0410-b5e6-96231b3b80d8