fix(build): describe git version from lightweight tags too

A USEGITVER=1 build derives its version with `git describe`, which only
considers annotated tags. xCAT tags releases with lightweight tags, so in a
tree without a reachable annotated tag `git describe` fails and VER comes out
empty, producing a broken package version.

Use `git describe --tags` so lightweight tags are considered.

Recovered from the unmerged lenovobuild branch (original 25248d19; the
commit's .post->.POST rename and its makegenesisbuilderrpm hunk are omitted
-- the former is an unrelated RPM-sort preference and the latter targets a
script no longer present on master).

Co-authored-by: Jarrod Johnson <10814490+jjohnson42@users.noreply.github.com>

buildcore.sh

@@ -195,7 +195,7 @@ fi
 
 function setversionvars {
     if [ ! -z "$USEGITVER" ]; then
-        VER=`git describe`
+        VER=`git describe --tags`
         VER=${VER/-/.post}
         VER=${VER/-/.}
     else