build: Determine release version with simple grep

build: Determine release version with simple grep

To determine what the release version is to be, use a simple grep over
the moxie.build file and cut off the `-SNAPSHOT` part. The moxie
tag command doesn't do anything else, either. But the problem is that
when using the moxie tag command on the release branch, where the
version has already been set to a release version, it would create
a second release version, like so: 1.9.2-1.