Not every package that needs xcbuild will want to use its build phase.
I have moved the xcbuild setup hook to the new attribute xcbuildHook.
This means that dontUseXcbuild is no longer needed. If you just need
to call xcbuild on its own you can just refer to xcbuild.
Also updates xcbuild version.
This changes the raw string expressions into nix expressions that are
then converted into json by builtins.toJSON. Then, converted to Plist
XML by Apple's plutil. Sadly, xcbuild does not support using raw JSON
but Apple's plutil does so we just convert the file from JSON to XML
using Apple's plutil. The result is not ideal but it looks like all OS X
systems have working plutil's.
- set mac version to 10.10
- add setup hook.
