Allow running mjsunit/manual-parallel-recompile on single-core systems.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 9211b56653f2bce095fe90262d2ad86252df3c34..08660e9790d96b8010b3df31127feee9d3a9b3a5 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -8070,6 +8070,13 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_RunningInSimulator) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_IsParallelSupported) {
+  HandleScope scope(isolate);
+  return FLAG_parallel_recompilation
+      ? isolate->heap()->true_value() : isolate->heap()->false_value();
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_OptimizeFunctionOnNextCall) {
   HandleScope scope(isolate);
   RUNTIME_ASSERT(args.length() == 1 || args.length() == 2);