NixOS with its nixpkgs [0] and cache [1] would also not work if compilers weren't reproducible. Though they won't use something like PGO or some specific optimization flags as these would very likely lead to unreproducible builds. For example most distros ship a PGO optimized build of Python while nixos does not.
[0] https://github.com/nixos/nixpkgs
[1] https://cache.nixos.org/