Add support for lib_dirs to gn_to_cmake.py.

The vulcan code uses lib_dirs to point to the libs in the SDK.

Change-Id: I4a1a4235b8534f3f937640b10f9758b0c70434c9
Reviewed-on: https://skia-review.googlesource.com/4003
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed