v0.7.4

nfs: non-root guest users can write the synced folder

Both nfs sync methods mapped only guest root to the host user who
launched anyvm. Any other guest account kept its own uid, so it could
write the share only when that uid happened to equal the host's.
FreeBSD's first pw useradd hands out 1001, the GitHub runner's uid, so
it worked there by luck; Solaris's useradd hands out 1000, and every
write failed with EACCES (vmactions/solaris-vm#70).

Every guest uid is now squashed to the launching user:

--sync sys-nfs the kernel nfsd export gets all_squash
--sync nfs the user-space nfsd moves to v0.1.1 and runs with
its new -all_squash

Files a non-root guest user creates are owned by you on the host, the
same as the ones guest root creates. Where anyvm has to start nfsd
under sudo (the BSD guests that need the portmapper on port 111), the
squash target is still the user who launched anyvm, not root.

The Hurd keeps its guest root unsquashed in both modes, because
/hurd/nfs chowns every new file to uid 0.

DragonFly BSD is a known exception: its NFS client checks a create or
delete against the parent directory's mode bits locally, before any
request reaches the server, so a non-root guest user still cannot
write a 0755 share it does not own, whatever the server would allow.

nfsd v0.1.1 also makes its permission checks match the Linux kernel
nfsd when nothing is squashed: owner override, read access to
execute-only files, sticky directories, and special stateids.

New default builder versions:

openbsd 2.1.0 -> 2.1.1 adds OpenBSD 8.0, now the default
release
openindiana 2.1.2 -> 2.1.4 gcc-14 is optimized again (oi-3), and
std::locale("") no longer crashes
(oi-4)

Other: CI checks that a non-root guest user can write the share with
both nfs methods, and refreshes the apt index when an install hits a
stale one.

Full Changelog: v0.7.3...v0.7.4