pre-commit auto remove trailing whitespace from `.mk` files (#377)

If there are too many changes / files I can create a smaller PR

Thanks

Port main/bean to gbuild.

Patch by: me



git-svn-id: https://svn.apache.org/repos/asf/openoffice/trunk@1847358 13f79535-47bb-0310-9956-ffa450edef68