Brought back the Standalone and Linker tests into backend.native:tests:run.

runtime/src/main/cpp/ReturnSlot.cpp

@@ -25,10 +25,12 @@ THREAD_LOCAL_VARIABLE long long storage;
 
 extern "C" {
 
+RUNTIME_USED
 KDouble ReturnSlot_getDouble() {
   return *reinterpret_cast<KDouble*>(&::storage);
 }
 
+RUNTIME_USED
 void ReturnSlot_setDouble(KInt upper, KInt lower) {
   reinterpret_cast<KInt*>(&::storage)[0] = lower;
   reinterpret_cast<KInt*>(&::storage)[1] = upper;