Move ConvertFileToHeaderWithCharacterArray.gypi from Source/core to Source/build

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

Review URL: https://codereview.chromium.org/26742002

git-svn-id: svn://svn.chromium.org/blink/trunk@159268 bbb929c8-8fbe-4397-9dbb-9b2b20218538