code: function cleanUpOldExecutable(next) {
          fs.unlink(nodeCompiler.releasePath, function(err) {
            if (err) {
              if (err.code === 'ENOENT') {
                next();
              } else {
                throw err;
              }
            } else {
              next();
            }
          });
        }
docs: If an old compiled executable exists in the Release directory, delete it.
  This lets us see if the build failed by checking the existence of this file later.