Makefile.local: have all files in release tarball be owned by root

Makefile.local: have all files in release tarball be owned by root

The tar content `git archive` creates (reproducibly) have owner and
group set to 'root'. (GNU) tar writes user ids to the added file
`version` by default. The contents of tar archive looks better and
more consistent when owner and group in all files are the same.

While at it, split this long command line to multiple lines.