This could be interesting. Maybe for the non-natively bootstrapped platforms, we could slightly modify the late stages of minimal-bootstrap such that the final gcc is optionally a cross compiler (build=x86_64, host=target=stdenv.buildPlatform) and minimal-bootstrap.*-static would be cross-compiled with it

There's a PoC bootstrap for aarch64-linux now: https://github.com/NixOS/nixpkgs/pull/487398 To make this work, I had to tell gcc-15 that the host is musl-based. But in fact this breaks building glibc on i686 (but not on x86_64). I think this might be the frankenstein gcc problem? So I guess we need a glibc already built before we build a proper gcc targeting glibc

Does anyone know where the fact that the Darwin stdenv builds CMake twice comes from? As far as I can tell, it's from stage 0, and then just gets used in the other stages from there. Am I missing something here, is it something with the overrides? It looks like it might be, but then the fact that those are only allowed in the final stage (per booter.nix) (when that doesn't seem true, since then they wouldn't be defined...?) comes up.

(Isn't this the same pattern (defining in one stage and referencing in the others) that makes Glibc only build a limited number of times in the Linux stdenv?)

You think cmake should be rebuild less? Or more?

glibc's is probably a bit different as it's a part of stdenv.cc.libc and mainly used by that I would guess. Also, if depends if the package is used or not by other packages in the derivation would affect rebuild count as well.