app: integrate fsu

This removes the dependency on external user switchers like sudo/machinectl and decouples fortify user ids from the passwd database.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

cmd/finit/main.go

@@ -103,7 +103,7 @@ func main() {
 	if err := cmd.Start(); err != nil {
 		fmsg.Fatalf("cannot start %q: %v", payload.Argv0, err)
 	}
-	fmsg.Withhold()
+	fmsg.Suspend()
 
 	// close setup pipe as setup is now complete
 	if err := setup.Close(); err != nil {