Use modern CMake about mos

[morganbengtsson]

Thanks, should be a bit cleaner now:
4a2efb8
95aa800
Quite sure I could read up on CMake a bit more though.

[Flamefire]

Related: Is (e.g.) glm a public dependency or is it only used internally?
There is add_definitions(-DGLM_FORCE_RADIANS) at the top, if glm is public you should use target_compile_definitions(target PUBLIC ...) if not use PRIVATE and make the include directory PRIVATE too. Similar for others in target_include_directories: Decide and define what is only internally used and what is included in the external interface.
-DMOS_EFX can also be a PRIVATE in target_compile_definitions