[CodeView] Revert 8374bf43 and...

[CodeView] Revert 8374bf43 and 403f9537

This reverts:
8374bf43 [CodeView] Fix generated command-line expansion in LF_BUILDINFO. Fix the 'pdb' entry which was previously a null reference, now an empty string.
403f9537 [CodeView] Add full repro to LF_BUILDINFO record

This is causing the lld/test/COFF/pdb-relative-source-lines.test to fail: http://lab.llvm.org:8011/builders/lld-x86_64-win/builds/1096/steps/test-check-all/logs/FAIL%3A%20lld%3A%3Apdb-relative-source-lines.test
And clang/test/CodeGen/debug-info-codeview-buildinfo.c fails as well: http://lab.llvm.org:8011/builders/clang-s390x-linux/builds/33346/steps/ninja%20check%201/logs/FAIL%3A%20Clang%3A%3Adebug-info-codeview-buildinfo.c