Add inputDerivation to enable binary caching

[amarshall]

Same rationale as upstream, see
NixOS/nixpkgs#95536

[brianmcgee]

@amarshall is this ready for review if it was updated with latest main?

[amarshall]

@brianmcgee should be, yes, I have rebased off latest and force-pushed. There were no conflicts.

[zimbatm]

Sorry, I should have reacted earlier; this change is not needed. Unlike upstream's mkShell, mkNakedShell was designed to be built or loaded as a nix-shell. This was part of the design, so you can nix-build the devshell, which has references to all the inputs. So instead of nix-build shell.nix -A inputDerivation | cachix push, you can already nix-build shell.nix | cachix push.

[amarshall]

@zimbatm Hmm, I remember I did this because some things weren’t getting uploaded to the cache as expected, but we’ve since changed to using a post-build hook instead anyway. I’ll try to reproduce.

[zimbatm]

Ok, let me know if you can build a repro

[zimbatm]

I'm going to assume that it was fine :)