stdenv and base packages: fix with __structuredAttrs enabled

[globin]

Description of changes

This fixes stdenv with __structuredAttrs enabled.

Test build:

nix-build -E 'with import ./. { config.structuredAttrsByDefault = true; }; hello'

• makeFlags is a bash array and cannot be appended to as done in glibc's preConfigure.
• env vars may only be strings and have to be in env to be exported
• substituteAll only reads and substitutes exported variables

This is the first part of a number of PRs that intend to make nixpkgs forward-compatible with __structuredAttrs enabled globally.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[Artturin]

You did a change in substitute-all.nix so this should be unnecessary now

[globin]

Thanks missed that one while rebasing!

[globin]

I think this is a good point, where I'll leave this PR and continue with follow-ups based on this:

• set of base packages upon stdenv works, including: systemd, nginx, postgresql, sway
• rust/perl/python language infrastructure generally works for an adequate number of packages

Next steps will probably be around go/ruby language infrastructure and "leafier" packages.

I've tried to make sure to not break anything with structuredAttrs kept off, although there are some larger changes, if any are controversial I can exclude them for now, to get this merged more easily.

[globin]

Found an issue with pytestFlagsArray which has been used different than all other *Array variables, which makes backward-compatibility difficult to achieve, might be a better option to break this option and fix it properly right away.