Review Linux section of CI build matrix

[heplesser]

While working on #2762, I noticed some points in the CI build matrix for Linux, which may deserve attention:

We first set

https://github.com/nest/nest-simulator/blob/7d9150c0bffd71e3fdce0318d94406303554045e/.github/workflows/nestbuildmatrix.yml#L401-L404

and then later change this to

https://github.com/nest/nest-simulator/blob/7d9150c0bffd71e3fdce0318d94406303554045e/.github/workflows/nestbuildmatrix.yml#L540

Shouldn't we set it in one place only?

Also, why do we have

https://github.com/nest/nest-simulator/blob/7d9150c0bffd71e3fdce0318d94406303554045e/.github/workflows/nestbuildmatrix.yml#L536-L538

where is NEST_BUILD_COMPILER set and why are we binding ourselves to clang-11, while the most recent version is 16.0?

Finally and unrelated, what is the purpose of this commented-out section (exists similarly for macOS):

https://github.com/nest/nest-simulator/blob/7d9150c0bffd71e3fdce0318d94406303554045e/.github/workflows/nestbuildmatrix.yml#L206

[github-actions[bot]]

Issue automatically marked stale!