Fix clang build failure

Apparently opinion is divided on whether [[noreturn]] is allowed on a
lambda: http://stackoverflow.com/questions/26888805/how-to-declare-a-lambdas-operator-as-noreturn

http://hydra.nixos.org/build/36462100

release.nix

@@ -99,6 +99,8 @@ let
 
         doInstallCheck = true;
         installCheckFlags = "sysconfdir=$(out)/etc";
+
+        stdenv = clangStdenv;
       });