First stab at iOS support.

Actually works quite well once you figure out how to produce the signing
keys!
Be explicit about the defaults.

Also use the right syntax, derp.
Use -D no-flash-override here, which is supposed to help AOT.

https://github.com/HaxeFoundation/haxe/commit/e17bd2bf5d6b046bdaa91f44091907a203e2d528