Use rules based c++ toolchain

[finn-ball]

Is your feature request related to a problem? Please describe.
The current toolchain definitions are long and verbose:
https://github.com/tweag/rules_nixpkgs/blob/master/core/private/cc_toolchain/cc_toolchain_config.bzl

Describe the solution you'd like
Use the new rules based toolchain, example here:
https://github.com/bazelbuild/rules_cc/tree/main/examples/rule_based_toolchain

[malt3]

Thank you for reaching out. I have seen the new, rules based approach and it looks very promising.
Without having looked at it at a deeper level, I’m not sure how much work this entails. I think we should consider doing this.

In any case, if you or someone else wants to take a stab, we are open to contributions.