make-wrapper should use runtimeShell, not $SHELL, for cross-compilation

[tathougies]

Motivation for this change

make-wrapper.sh is used to wrap python programs (and others perhaps). Write now it uses the value of $SHELL to get the shell it should use to build its wrapper. However, this only works if the shell being used is the same one as the shell the script will be executed under. This assumption does not hold for cross-compilation. Without this patch, cross-compiled python scripts get a shebang asking to be executed using the build architecture's shell.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• 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 nox --run "nox-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)
• Fits CONTRIBUTING.md.

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[grahamc]

Seems too vague to be true: wrappers may be executed in the build context too. No?

[tathougies]

@grahamc sure, but you should be using buildPackages for wrappers that will be used in build context, in which case runtimeShell would be the build machine runtime shell.

[Ericson2314]

Good catch!

[Ericson2314]

Switched to staging