*WIP* OSX Binary build scripts and changes

Not for merging yet. This is more to show that I'm working on the OSX Binary build scripts and also a RFC on the code/scripts that it meets the required standards (I've been away for a while, and I've had to rebuild my build chain as well).

I've removed the dependancy of XCode to create binaries which should make it nice and simple to automatically generate nightly builds now.

scripts/build-osx.sh is intended to be hooked in from another 'master' build script (as suggested by @robn) as it may live on a different machine.

Comments and feedback welcome.