A. Checkout the developer version of JUCE
git clone -b develop https://github.com/WeAreROLI/JUCE.git
(For consequent updadets, you just need to)
git checkout develop; git fetch; git pull
B. Build Projucer, where JUCE is the root of your clone
xcodebuild -project JUCE/extras/Projucer/Builds/MacOSX/Projucer.xcodeproj
b. Optionally build DemoRunner and AudioPluginHost