STM32F746 Discovery demonstration project does not compile
It does not build for me either - different errors but related to the same module.
You need to try the ST forum, this is not an ac6 error. They don’t have all the code saved with their example.
(You do know you don’t have to build the code, the hex file is available. But to program it you need the ST-LINK utility and an external loader configured.)
-Matt