Remove clang11Stdenv

[9999years]

Motivation

Clang 11 doesn't have support for three-way-comparisons (<=>, "spaceship operator", "consistent comparisons") and is older than clangStdenv.

Let's remove clang11Stdenv, keeping the default clangStdenv.

Context

The clang11Stdenv was added in #4996

clangStdenv is currently 12 on FreeBSD and Android and 16 on other platforms:

https://github.com/NixOS/nixpkgs/blob/32e718f00c26c811be0062dd0777066f02406940/pkgs/top-level/all-packages.nix#L16629-L16644

Let's start by removing Clang 11 from our distribution. Next we can consider upgrading to Clang 17, which fully supports the spaceship operator:

https://releases.llvm.org/17.0.1/tools/clang/docs/ReleaseNotes.html#what-s-new-in-clang-release

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[abathur]

I'm not certain it implies anything about this specific change, but just in case: after the recent nixpkgs stdenv bump to llvm 16, the nixpkgs builds of Nix are segfaulting on intel macs running some macOS versions (I believe we know 10.14, 10.15, 11.x, and I think there was also a report for 12.x).

So far, none of the release Nix builds used by the installer are affected by this, but I would guess the problem will get noisier if that happens :)

We've made slow headway on figuring out why and how to fix it, but it hasn't quite turned into PRs. See:

• segfault during substitution on x86-64_darwin #9640
• libcxx-{15,16,etc} segfault when multiple libcxx loaded nixpkgs#269548

[9999years]

@abathur That's interesting, but I don't think it's related here — Nixpkgs doesn't use the Nix packages defined in this repo and instead defines their own build expressions which always use the default stdenv:

https://github.com/NixOS/nixpkgs/blob/32e718f00c26c811be0062dd0777066f02406940/pkgs/tools/package-management/nix/common.nix#L77