Ok, build completed overnight and it works!
Well, the web interface doesn't, but that's another issue.
The Alpine-based binary seems to work (as in not crash) as well.
Will fiddle around a bit more once I don't have to SSH from the phone...
Edit:
...
$ ./pihole-FTL-armv6 -v
vDev-04269f3
$ pihole-FTL -v
v5.23-1063-gce9fd82a
...
Edit 2: I'm also looking into upgrading to a Zero 2W once they are available at normal prices again, then you could have mine.