unify size of enums between rust and C

[TychoVrahe]

By default, ARM eabi has -fshort-enums switched on, so we need to pass this flag to clang when building bindings for rust to account for this behavior.

For contrast, unix builds don't use this. SDL also enforces building without this flags via static asserts, so we can't use -fshort-enums for the whole of unix, so i opted for using different settings for unix and embedded targets.

[github-actions]

core UI changes	device test	click test	persistence test
T2T1 Model T	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
T3B1 Safe 3	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
T3T1 Safe 5	test(screens) main(screens)	test(screens) main(screens)	test(screens) main(screens)
All	main(screens)