Move core/scripts/list_idl_files_with_partial_interface.py to build.

R=abarth@chromium.org
BUG=297477

Review URL: https://codereview.chromium.org/26858002

git-svn-id: svn://svn.chromium.org/blink/trunk@159347 bbb929c8-8fbe-4397-9dbb-9b2b20218538