supercollider: build with alsa (midi) support on non-darwin

[yurkobb]

Motivation for this change

MIDI functionality is very important in real time sound synthesis packages like SuperCollider, and other linux distributions build SuperCollider with MIDI support.

Things done

Added alsaLib input on non-darwin, effectively enabling Midi support on Linux.

• 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 (Fedora)
• 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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[Mic92]

cc @magnetophon

[magnetophon]

lgtm!