emulator/qemu-user-static: fix major regression from signal refactor

Excellent diagnosis by Andrew Gierth revealed the exact nature of the
regression from previous signal handling fixes; gobject-introspection now
builds, and we should be able to once again build a pretty large chunk of
the ports tree.

The configure script patch has been incorporated into our tree, so the patch
may be removed.

As mentioned previously, qemu-user-static and qemu-user-static-devel will
not always be updated in lockstep; future changes will land to
qemu-user-static-devel first followed by qemu-user-static.