Fixed replacements for files with relative paths are not applied.

Replacements were no applied when using a compilation database with paths in the
compilation command relative to the compile directory. This patch makes those
paths abosulte.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191776 91177308-0d34-0410-b5e6-96231b3b80d8