Tweak sort order of tags in get-version.

We want to sort such that the most recent/relevant tag is first
and gets used to set the compiled-in version.

The solution is far from general, but works for the tag formats
used by dnsmasq. v2.84 sorts before v2.83, but v2.83 sorts
before v2.83rc1 and 2.83rc1 sorts before v2.83test1
1 file changed