sox: added enableLibpulseaudio option

[elitak]

Motivation for this change

Added libpulseaudio features to build so pulse sources can be used at runtime.

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• 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/)
• Fits CONTRIBUTING.md.

---

[mention-bot]

@elitak, thanks for your PR! By analyzing the history of the files in this pull request, we identified @edolstra, @taku0 and @MarcWeber to be potential reviewers.

[MarcWeber]

most other packages (eg mplayer) call it pulseSupport. Maybe consistent naming makes sense.

[elitak]

All the names in here are a bit nonstandard; I was just trying to maintain file-level consistency. I agree they should be renamed. This PR is merged now though, so I suggest just creating a new PR to change them all, if you're so inclined.

[MarcWeber]

You're right. Just wondering whether it makes sense to introduce a global config.pulseSupport option which can be used by all packages -> then I was told that pulse is going to work with mplayer even without pulse support and that using flags would mean having binary cache misses. Imean there are many packages which can be compiled with gkt/qt (gentoo useflag like). The question is does it make sense to introduce/document such. -> will ask on mailinglist.