Enable g++ O3 optimization

c++ x 0.24 ops/sec ±2.91% (6 runs sampled)
java x 0.23 ops/sec ±1.35% (6 runs sampled)
node.js x 0.14 ops/sec ±3.07% (5 runs sampled)
node.js is slower than c++ by 69.51%
node.js is slower than java by 58.89%