cmake: Tighten deps

[Ericson2314]

Motivation for this change

• OpenSSL is evidentally an optional dep. I guess pkg-config found it
  before because it was a transitive dep?

• zstd and cross-built CMake can get by with a `cmakeMinimal that we
  use during bootstrapping, so let's restrict to that.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[FRidh]

Don't we put overrides for bootstrapping elsewhere?

[vcunat]

If it's more complex, I think it's better to keep an option in the expression itself, as it's less likely that a change will clash with those overrides.

EDIT: though here it just switches defaults to other parameters (and pname which seems a nit). Still, removing the parameter should be a separate commit and maybe even separate PR (doesn't seem important to me anyway).

[Ericson2314]

Yeah the Darwin bootstrapping just used the isBootstrap defined here.

[Ericson2314]

Ofborg is stalled, but I built the Darwin stdenv by hand.

[vcunat]

Ofborg for darwin is a "known problem": NixOS/ofborg#529 (comment)