nix: use curl with c-ares resolver

[orivej]

Motivation for this change

This is an alternative to #41452. Apparently curl threaded resolver enabled in 7.60 imposes additional restrictions on usage of its API that are not present with its blocking or asynchronous resolvers.

Building with c-ares makes the asynchronous resolver the default.

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/)
• Fits CONTRIBUTING.md.

Tested nix-channel --update does not wait for 10 seconds for DNS resolution.

[orivej]

@GrahamcOfBorg build nix

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: nix

Partial log (click to expand)

running test tests/fetchGit.sh... [SKIP]
running test tests/fetchMercurial.sh... [SKIP]
running test tests/signing.sh... [PASS]
running test tests/run.sh... [PASS]
running test tests/brotli.sh... [PASS]
running test tests/pure-eval.sh... [PASS]
running test tests/check.sh... [PASS]
running test tests/plugins.sh... [PASS]
All tests succeeded
/nix/store/kkfcf5mlg95iffxi1s3clvxjgqfk6v08-nix-2.0.4

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: nix

Partial log (click to expand)

/nix/store/kkfcf5mlg95iffxi1s3clvxjgqfk6v08-nix-2.0.4

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: nix

Partial log (click to expand)

running test tests/fetchGit.sh... [SKIP]
running test tests/fetchMercurial.sh... [SKIP]
running test tests/signing.sh... [PASS]
running test tests/run.sh... [PASS]
running test tests/brotli.sh... [PASS]
running test tests/pure-eval.sh... [PASS]
running test tests/check.sh... [PASS]
running test tests/plugins.sh... [PASS]
All tests succeeded
/nix/store/45m9fdwbnxzdbxgmk5pd6a7d9lwxkk8k-nix-2.0.4

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: nix

Partial log (click to expand)

these derivations will be built:
  /nix/store/5nybl513gkixidz0qkgnhvnp7qihy5is-curl-7.60.0.drv
  /nix/store/4d9mcfyxgldgg9m8mh4zkqqmlsycqd65-nix-2.0.4.drv
waiting for locks or build slots...
/nix/store/45m9fdwbnxzdbxgmk5pd6a7d9lwxkk8k-nix-2.0.4

[GrahamcOfBorg]

Success on x86_64-darwin (full log)

Attempted: nix

Partial log (click to expand)

running test tests/fetchGit.sh... [SKIP]
running test tests/fetchMercurial.sh... [SKIP]
running test tests/signing.sh... [PASS]
running test tests/run.sh... [PASS]
running test tests/brotli.sh... [PASS]
running test tests/pure-eval.sh... [PASS]
running test tests/check.sh... [PASS]
running test tests/plugins.sh... [PASS]
All tests succeeded
/nix/store/6xpa5j1l0wwpwryky8agd4fnwv0n699h-nix-2.0.4

[GrahamcOfBorg]

Success on x86_64-darwin (full log)

Attempted: nix

Partial log (click to expand)

running test tests/fetchGit.sh... [SKIP]
running test tests/fetchMercurial.sh... [SKIP]
running test tests/signing.sh... [PASS]
running test tests/run.sh... [PASS]
running test tests/brotli.sh... [PASS]
running test tests/pure-eval.sh... [PASS]
running test tests/check.sh... [PASS]
running test tests/plugins.sh... [PASS]
All tests succeeded
/nix/store/6xpa5j1l0wwpwryky8agd4fnwv0n699h-nix-2.0.4

[dtzWill]

I like this a lot, but c-ares means no support for glibc's nss plugins that are sometimes used for mdns/NIS/maybe-other-things.

I don't know how important that is for fetchurl, or if such things are expected to work with Nix (presumably they wouldn't in a sandbox, so only builtins.fetchurl?), but thought I'd mention it.

[orivej]

@dtzWill Sounds reasonable, closing in favor of #41619.