emulators/qemu-user-static{,-devel}: unbreak after base r355641

r355641 added sigorset to base, which collides with sigorset in
qemu-user-static. This is effectively a patch (applied in the qemu-bsd-user
repo) that makes the qemu version private and uses that for now, until
sigorset in FreeBSD stabilizes across older branches.

Approved by: 0mp (ports)