[PATCH] Fix replacements for files with relative paths are not applied.

[Ariel Bernal]

  A better look at make_absolute showed me that it doesn't check for the filepath to exists it just gets the current path (PWD) and then uses the current path for getting the root and relative paths, and append them to the file name. So you can actually get an absolute path to a virtual file :).
  I think virtual files shouldn't be made absolute unless someone explicitly create them that way.

http://llvm-reviews.chandlerc.com/D1800