Full build documentation for SpiderMonkey is hosted on MDN:
  https://developer.mozilla.org/en-US/docs/SpiderMonkey/Build_Documentation

Note that the libraries produced by the build system include symbols,
causing the binaries to be extremely large. It is highly suggested that `strip`
be run over the binaries before deploying them.

Building with default options may be performed as follows:
  cd js/src
  ./configure
  make