Add macOS simulator build to pipelines

[KenVanHoeylandt]

Build the macOS simulator.
We can't publish it yet, because macOS requires SDL window creation to happen from the main thread, but that in its turn requires the event loop on the main thread too, which isn't working currently:

• a blocked white screen when event loop is on main thread
• a black screen when event loop is on a FreeRTOS task (but invisible UI is clickable and starts apps)

Changes in this PR:

• GitHub actions changed to build simulator on macOS (it's broken, but at least we get a good code portability check for now!)
• Buildscripts/ shell scripts updated to use /bin/sh so it works on macOS too
• Various includes fixed in various subprojects so the code is more portable