build: Don't use external script to set version

build: Don't use external script to set version

The meson documentation points out the the version string should be a
fixed string. Our trick with trying to figure out the version is not
working in all cases, e.g. 'meson dist' will create a wrong file name.

The idea is to update the version string when a new development cycle
starts and mark the release with a tag. This is what other projects
do as well. Let's follow their common practice.

Signed-off-by: Daniel Wagner <dwagner@suse.de>