Add master and lollipop OS X environment details

The master branch is currently buildable on OS X 10.8-10.10 with Xcode
4.5.2-6.1, but Lollipop is only buildable on OS X 10.8 with Xcode 4.5.2.
This patch adds in the information to the OS X build environment section
to reflect this.

Change-Id: Ib99a6f717d3d5f0086b7e6f32023e0aace9dae8b
1 file changed