switch core support

add nekobox_core

linux: use sing-box for vpn

main/main.cpp

@@ -67,6 +67,7 @@ int main(int argc, char *argv[]) {
             return 0;
         }
     }
+    release_runguard = [&] { guard.release(); };
 
     // icons
     QIcon::setFallbackSearchPaths(QStringList{