fix-build: add compiler min version checks

[JasonQiu1]

Before luxcore builds, ensure minimum version for compiler is met:

• gcc: >= 14
• LLVM/Clang: >= 20
• MSVC : >= 1940

Closes #676 and #675.

[howetuft]

Hello,
Thank you very much! It looks really better to me: all platforms are addressed now and the plumbing of finding tool versions is delegated to Cmake, which provides on-the-shelf support for that!

One very important thing however (sorry, I was travelling yesterday and I missed this essential point): can you please target for_v2.11 rather than master?. v2.10 is frozen now (and master too). If needed, we will backport to for_v2.10.0. Thank you!

[JasonQiu1]

All good, I changed the base branch to for_v2.11!

[howetuft]

Thank you!