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

test/mjsunit/manual-parallel-recompile.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 42 matching lines @@
 }
 
 f(g(1));
 assertUnoptimized(f);
 assertUnoptimized(g);
 
 %OptimizeFunctionOnNextCall(f, "parallel");
 %OptimizeFunctionOnNextCall(g, "parallel");
 f(g(2));  // Trigger optimization.
 
-assertUnoptimized(f);  // Not yet optimized.
-assertUnoptimized(g);
+if (%IsParallelRecompilationSupported()) {
+  assertUnoptimized(f);  // Not yet optimized.
+  assertUnoptimized(g);
+}
 
 %CompleteOptimization(f);  // Wait till optimized code is installed.
 %CompleteOptimization(g);
 
 assertOptimized(f);  // Optimized now.
 assertOptimized(g);