Allow running gn_to_bp.py from another script

Use __file__ to determine where 'here' is.

Necessary for
https://chrome-internal-review.googlesource.com/313075.

Change-Id: I1b9571847c761da311012039e2c885fad0a593cb
Reviewed-on: https://skia-review.googlesource.com/6230
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed