Building cvmfs on alpine linux "musl" not "glibc"

I’ve quickly tried to build GitHub - resslinux/libexecinfo from source and that seems to work - although I would not use this in production, in the end it’ll likely be better to patch out execinfo alltogether.

Going on to compile, I’ve hit
https://inbox.vuxu.org/musl/20220412182436.519e76e5598d272e7a1afada@zhasha.com/T/

and

https://bugs.gentoo.org/717542

but gcc seems happy with the workaround that can luckily also be found in those links.