The compiler setting in the xcodeproj is overridden by the CC setting in the environment. This is a bit insane IMO since the xcodeproj itself has detailed decisions about what tools to use.
FixesHomebrew/homebrew#6406.
* Install the Mogenerator default templates & provide instructions for
copying them into "~/Library/Application Support/mogenerator".
* Force the use of Clang.
Signed-off-by: Adam Vandenberg <flangy@gmail.com>