Some relevant links would be
- Julia 1.6.0 · Issue #116697 · NixOS/nixpkgs · GitHub
- Refactor julia 1.6 by cstich · Pull Request #118483 · NixOS/nixpkgs · GitHub
- julia_10-bin, julia_16-bin: add x86_64-darwin support · Issue #123394 · NixOS/nixpkgs · GitHub
- julia fails to build on macos · Issue #114766 · NixOS/nixpkgs · GitHub
- Build julia 1.5 on macos by idontgetoutmuch · Pull Request #114855 · NixOS/nixpkgs · GitHub
- julia_16: alias to julia_16-bin by samuela · Pull Request #123395 · NixOS/nixpkgs · GitHub
There may be others but these are a good place to start.