mateamt: hack around new default.nix

mateamt.nix

@@ -2,12 +2,24 @@
 }:
 with pkgs;
 let
-  mateamt = haskellPackages.callPackage <mateamt/shell.nix>;
+  mateamtSrc = stdenv.mkDerivation {
+    name = "mateamt-src";
+    src = <mateamt>;
+    phases = [ "unpackPhase" "patchPhase" "installPhase" ];
+    patchPhase = ''
+      substituteInPlace default.nix \
+        --replace \
+        "builtins.fetchTarball https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz" \
+        "<haskell-nix>"
+    '';
+    installPhase = "cp -ar . $out";
+  };
+  mateamt = haskellPackages.callPackage "${mateamtSrc}/shell.nix";
   ghcBlacklist = [
-    "ghc822"
-    "ghc844"
-    "ghc881"
-    "ghcHEAD"
+    # "ghc822"
+    # "ghc844"
+    # "ghc881"
+    # "ghcHEAD"
   ];
   ghcVersions =
     builtins.filter (p: