haskellPackages.djinn: apply patch for GHC 8.4

pkgs/development/haskell-modules/configuration-common.nix

@@ -688,6 +688,13 @@ self: super: {
     sha256 = "1m2d47ni4jbrpvxry50imj91qahr3r7zkqm157clrzlmw6gzpgnq";
   });
 
+  # Djinn's last release was 2014, incompatible with Semigroup-Monoid Proposal
+  # https://github.com/augustss/djinn/pull/8
+  djinn = appendPatch super.djinn (pkgs.fetchpatch {
+    url = https://github.com/augustss/djinn/commit/6cb9433a137fb6b5194afe41d616bd8b62b95630.patch;
+    sha256 = "0s021y5nzrh74gfp8xpxpxm11ivzfs3jwg6mkrlyry3iy584xqil";
+  });
+
   # We cannot build this package w/o the C library from <http://www.phash.org/>.
   phash = markBroken super.phash;