CI: Target the tested architecture, not `-march=native`
From [here](https://i10git.cs.fau.de/pycodegen/pystencils/-/merge_requests/439#note_35954): > When testing certain vector architectures, we should configure the JIT-compiler to not target -march=native, but whatever ISA we're testing, such that these errors can be found also on a system with a more recent version of AVX.
issue