Fix execution of post install scripts on cross builds

Add missing call to register_binfmt before installing packages on
mkrootfs.

lib.sh.in

@@ -242,7 +242,7 @@ register_binfmt() {
     # use the static one always and make sure it shows up at the same
     # place in the host and the chroot.
     if [ ! -x "$ROOTFS/usr/bin/$QEMU_BIN" ] ; then
-        cp -f "$(which "$QEMU_BIN")" "$ROOTFS/usr/bin" ||
+        install -m755 -D "$(which "$QEMU_BIN")" "$ROOTFS/usr/bin/$QEMU_BIN" ||
             die "Could not install $QEMU_BIN to $ROOTFS/usr/bin/"
     fi
 }

mkrootfs.sh.in

@@ -136,8 +136,10 @@ run_cmd_target "xbps-install -S $XBPS_CONFFILE $XBPS_CACHEDIR $XBPS_REPOSITORY -
 # so we set this here.
 chmod 755 "$ROOTFS"
 
-# The pseudofs mountpoints are needed for the qemu support in cases
-# where we are running things that aren't natively executable.
+# The binfmt setup and pseudofs mountpoints are needed for the qemu
+# support in cases where we are running things that aren't natively
+# executable.
+register_binfmt
 mount_pseudofs
 
 # With everything setup, we can now run the install to load the