8292847: Zero: Allow ergonomics to select the GC

Reviewed-by: tschatzl, stuefe

src/hotspot/share/runtime/arguments.cpp

@@ -3152,6 +3152,12 @@ jint Arguments::finalize_vm_init_args(bool patch_mod_javabase) {
 #ifdef ZERO
   // Zero always runs in interpreted mode
   set_mode_flags(_int);
+
+  // Zero runs without compilers. Do not let compiler selection code
+  // to force it into Serial GC, let the GC ergonomics decide.
+  if (FLAG_IS_DEFAULT(NeverActAsServerClassMachine)) {
+    FLAG_SET_ERGO(NeverActAsServerClassMachine, false);
+  }
 #endif
 
   // eventually fix up InitialTenuringThreshold if only MaxTenuringThreshold is set