A few beginner questions

[ErikTempelaarVO]

I'm just starting out with CMake and I thought it would be a good idea to use best practices for the project's compiler warnings so I ended up here. 👋

I'm having trouble with some things and I hope this Q&A can shed some light on how things are supposed to be done.

1. My GCC 7.2.0 doesn't support all the warnings that are enabled. Should I set CLANG_WARNINGS manually to leave this particular warning out?
   (-Wextra-semi was added in 8.0 https://github.com/pkolbus/compiler-warnings/blob/main/gcc/warnings-top-level-8.txt)
2. My compiler is detected as unicode, but having this enabled breaks my build. Is there a way to control this auto-detection?
3. I'm cross-compiling from Linux to Windows using MXE, I invoke a custom cmake by MXE, that already loads a toolchain-file, should I configure cross-compiling in the CMakeLists.txt again for project_options?
4. MXE also includes ccache, and this works implicitly, but it is not detected as such. Anything I can do about that?

Oh, btw, I noticed that the links to the licences in the readme.md are broken