nix-eval-jobs: compile with Clang

GCC still ICEs on coroutines, while Clang works properly. Use the latter, just
like for Lix itself.

Change-Id: I802d6df7279550a5f5355e6c1ea0533c6a6a6964

flake.nix

@@ -228,6 +228,7 @@
           };
 
           nix-eval-jobs = final.callPackage ./subprojects/nix-eval-jobs {
+            stdenv = currentStdenv;
             srcDir = ./subprojects/nix-eval-jobs;
           };
 

subprojects/nix-eval-jobs/default.nix

@@ -14,6 +14,9 @@
   boost,
 }:
 
+# gcc ICEs on coroutines at least until 14.3, possibly longer
+assert stdenv.cc.isClang;
+
 let
   sourceBase = if srcDir == null then ./. else srcDir;
   package = stdenv.mkDerivation (finalAttrs: {