cmake: Simplify ccache logic

[diizzyy]

• Use USE_CCACHE switch, this seems to be a more common option having a quick look using Google
• Make use of find_program() functionality introduced in CMake 3.18 to simplify code

[diizzyy]

I think the "most" correct way would be to rip it out completely and leave it up to the user compiling it or the framework to specify rather than blindly looking for a binary. https://stackoverflow.com/questions/1815688/how-to-use-ccache-with-cmake Edit: Engrish ;-)

I can go either way :)

[sjaeckel]

I think the "most" correct way would be to rip out of completely and leave it up to the user compiling it or the framework to specify it

Thanks, that's exactly what we should do.

Do you wanna modify this PR to simply drop it or should I?

[diizzyy]

I'll update the PR, thanks! :)

[diizzyy]

Updated

[sjaeckel]

"Backported" via 5410d0bfbfb804b08b7b789a893d76d1fb2f720d