Merge pull request NixOS#7089 from NixOS/mention-accept-flake-config-…

…in-warning

Mention `--accept-flake-config` in the related warning

src/libexpr/flake/config.cc

@@ -68,7 +68,7 @@ void ConfigFile::apply()
                 }
             }
             if (!trusted) {
-                warn("ignoring untrusted flake configuration setting '%s'", name);
+                warn("ignoring untrusted flake configuration setting '%s'.\nPass '%s' to trust it", name, "--accept-flake-config");
                 continue;
             }
         }