Diagnostics from modules do not have a `main-file` listed. Tweak `clang-parse-diagnostics-file` to patch this up. Previously, the call to `os.path.basename` would crash. Radar-Id: rdar://problem/59000292
- Also, don't print headers if we aren't going to print any diagnostics. llvm-svn: 170973
llvm-svn: 143525