Makefile: Add helper targets for `branch` and `tag`

Add `branch` and `tag` targets to assist maintaining a checked-in
`versioninfo.inc`. The version, for branch and tag names, is given
as RELEASE on the command line, e.g.

  $ make branch RELEASE=1.0.x

Change-Id: Ieaa125e5168c5ce1d1aa3bb6857c648aa0c43ede
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/71779
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
1 file changed