packaging: remove workaround for clang stdenv asserts

This workaround was for the stdenv not being set when callPackage'ing
package.nix for some of the stranger CI outputs.

Change-Id: I2acdd6efa721b90dd3cb04358544d25d591ff084

flake.nix

@@ -269,6 +269,8 @@
             nix = pkgs.callPackage ./package.nix {
               inherit versionSuffix officialRelease buildUnreleasedNotes;
               inherit (pkgs) build-release-notes;
+              # Required since we don't support gcc stdenv
+              stdenv = pkgs.clangStdenv;
               internalApiDocs = true;
               busybox-sandbox-shell = pkgs.busybox-sandbox-shell;
             };
@@ -326,6 +328,8 @@
               inherit (nixpkgs) pkgs;
             in
             pkgs.callPackage ./package.nix {
+              # Required since we don't support gcc stdenv
+              stdenv = pkgs.clangStdenv;
               versionSuffix = "";
               lintInsteadOfBuild = true;
             };

package.nix

@@ -112,7 +112,7 @@
 }:
 
 # gcc miscompiles coroutines at least until 13.2, possibly longer
-assert stdenv.cc.isClang || lintInsteadOfBuild || internalApiDocs;
+assert stdenv.cc.isClang;
 
 let
   inherit (__forDefaults) canRunInstalled;
@@ -274,6 +274,10 @@ stdenv.mkDerivation (finalAttrs: {
     ++ lib.optionals lintInsteadOfBuild [
       # required for a wrapped clang-tidy
       llvmPackages.clang-tools
+      # load-bearing order (just as below); the actual stdenv wrapped clang
+      # needs to precede the unwrapped clang in PATH such that calling `clang`
+      # can compile things.
+      stdenv.cc
       # required for run-clang-tidy
       llvmPackages.clang-unwrapped
     ];