Revert 86551 (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns ou...

Revert 86551 (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) (turns out testers run `gclient sync` as well, and there are 10.5 testers) - grit_info: Explicitly make __file__ relative to the current directory.

__file__ is relative if grit_info is called like `python ../tools/grit/grit_info.py`,
but not if it's invoked from python code like `import grit_info; grit_info.DoMain()`.
And that confuses the xcode project generator, which will complain about hash
collisions if these paths are serialized in absolute form.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/7066030

TBR=thakis@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86557