This incorporates the build system changes to upgrade to SM52.
You will need to download the tarball at https://github.com/wraitii/0ad/blob/sm52/libraries/source/spidermonkey/mozjs-52.9.1pre1.tar.bz2
Test the full branch at https://github.com/wraitii/0ad/tree/sm52.
Patch by @Itms
Part of the SM52 migration.