Move away from static-haskell-nix

[robx]

We currently build a static PostgREST executable using https://github.com/nh2/static-haskell-nix. I think we should try moving away from that because

• the project appears to be abandoned
• the dependency makes it very difficult to upgrade nixpkgs

(This isn't really a new idea, I just wanted to file a central issue for tracking this.)

Some references:

• static build is broken #2327
• Fully static Haskell executables - overview issue NixOS/nixpkgs#43795
• Provide middle-ground overlay between pkgsMusl and pkgsStatic NixOS/nixpkgs#61575
• https://discourse.haskell.org/t/portable-haskell-executables-anyone-doing-that-possibly-using-nix/4816
• experiment: try using nix's pkgs.pkgsStatic for the static build #2332

[robx]

I've done a bit of digging into pkgs.pkgsStatic today:

• lz4: fix static build NixOS/nixpkgs#191915
• static build of postgresql (and thus libpq) fails NixOS/nixpkgs#191920

It looks like pkgsStatic goes quite a bit further than what we need to build a static PostgREST -- it builds a fully static package set, so it requires all PostgREST dependencies to build in a fully static environment, while all we need is the static build artifacts of all dependencies. E.g., this builds postgresql in an environment where only static libraries exist, which the build system seems not prepared for. We only need dontDisableStatic = true for our dependencies.

[benz0li]

The glcr.b-data.ch/ghc/ghc-musl images may be an alternative.
👉 https://github.com/benz0li/ghc-musl

[robx]

static-haskell-nix has recently seen some work again, with an update to nixos-23.05: nh2/static-haskell-nix#116