[PATCH] [clang] PR21195: Emit .gcno files to the proper location.

[Dan Albert]

Justin LGTM'd in mailing list.

Also discussed on mailing list: I plan to extend FileCheck to be able to handle --define PWD=`pwd` so that I can more accurately test that the .gcno file gets created in the current directory in the case of not passing -o.

http://reviews.llvm.org/D5697