.file filenumber "directory" "filename"
This removes one join+split of the directory+filename in MC internals. Because
bitcode files have independent fields for directory and filenames in debug info,
this patch may change the .o files written by existing .bc files.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142300 91177308-0d34-0410-b5e6-96231b3b80d8