It seems that when compiling using guix, obj/build.h ends up being
/ No build information available
which leads to the version being -unk. It would be nice to be able to tag it with the GIT_COMMIT_ID and with -dirty when appropriate.
I see some related discussion here for gitian: https://github.com/bitcoin/bitcoin/pull/18349/commits/80190e7aeb7e730934271b03918640ec18a56dc5