build: allow to run prebuild outside of this project.

pkg/prebuild/builder/userspace.go

@@ -27,7 +27,7 @@ func init() {
 	RegisterBuilder(&Userspace{
 		Base: prebuild.Base{
 			Keyword: "userspace",
-			Msg:     "Bypass userspace tools restriction",
+			Msg:     "Resolve variable in profile attachments",
 		},
 	})
 }

pkg/prebuild/cli/cli.go

@@ -73,10 +73,10 @@ func Prebuild() {
 		return
 	}
 
-	if full {
+	if full && paths.New("apparmor.d/groups/_full").Exist() {
 		prepare.Register("fsp")
 		builder.Register("fsp")
-	} else {
+	} else if prebuild.SystemdDir.Exist() {
 		prepare.Register("systemd-early")
 	}