As I'm unable to proceed on Windows 10 while you're working on build stuff for Grapefruit Juce, I've switched to Mac and I've got the same issue mentioned here.
You said to set compatibility level to pre-10.11. How do I do this? Is this something I do in Xcode? In Juce? In Mac OS settings?
Will this also deal with fatal errors "enumerator value evaluates to -2147483648, which cannot be narrowed to type 'uint32_t' (aka unsigned int)"?
I have tried going to the Config tab > XCode (MacOSX) and setting the OSX Deployment target to 10.10 but this doesn't change anything so I'm probably looking at the wrong thing.
As a newbie to Juce, this is frustrating as I've been unable to get started in either Windows 10 or OS X El Capitan so far. :-(