Stop passing %{release} to meson when building in upstream mode
    
    When building in upstream mode, the release doesn't really have any
    meaning so let's stop passing it as part of the version-tag and
    shared-library-tag arguments.
    
    This also makes it possible to make the release a timestamp so that
    each package built from upstream is guaranteed to be newer. If we
    pass the release to meson via version-tag and shared-library-tag and
    the release changes every build, we end up having constant rebuilds
    of various targets in meson that depend on the version.