<third_party/WebKit> FIXUP: Prevent a python IOError on Windows

The scripts for generating and aggregating the v8 bindings all suffer
from an IOError on Windows when doing a shadow build that results in
very large relative paths being used in the generated GYP actions.

Change-Id: I86f57fc94e8ff633e2499a08b8cafa7df9b39210
Reviewed-by: Michael Bruning <michael.bruning@digia.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>