ghc-8.4.3: minor fixes for cross-musl, same as used with 8.2.2

[dtzWill]

Patches are no longer needed, seem to be more or less upstreamed.

Fixes at least x86_64 cross-compilation to musl!

cc #37598

• 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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[matthewbauer]

Can you put these two changes into HEAD & maybe also ghc822?

[dtzWill]

And x86_64-linux-gnu -> aarch64-linux-musl ! \o/

I'll look into doing similar for HEAD--822 should already work (and have these changes), see #37598 (that originally made the changes in this PR to 8.4.2 but those were lost in update or something).

I didn't make the ncurses/etc change since it didn't seem necessary for the configurations I was testing this time 'round, presumably addressed upstream :).