Move core/scripts to build/scripts so that platform can use them.

R=abarth@chromium.org, eseidel@chromium.org
BUG=297477

Review URL: https://codereview.chromium.org/26414004

git-svn-id: svn://svn.chromium.org/blink/trunk@159266 bbb929c8-8fbe-4397-9dbb-9b2b20218538