merge-after-ci: move away from writePython3Bin

this is one is doing checks we don't want because we already have ruff.

pkgs/merge-after-ci/default.nix

@@ -1,6 +1,8 @@
 {
+  stdenv,
+  makeWrapper,
+  python3,
   bash,
-  callPackage,
   coreutils,
   git,
   lib,
@@ -10,22 +12,37 @@
   tea-create-pr,
   ...
 }:
-let
-  writers = callPackage ../builders/script-writers.nix { };
-in
-writers.writePython3Bin "merge-after-ci" {
-  makeWrapperArgs = [
-    "--prefix"
-    "PATH"
-    ":"
-    (lib.makeBinPath [
-      bash
-      coreutils
-      git
-      nix
-      openssh
-      tea
-      tea-create-pr
-    ])
-  ];
-} ./merge-after-ci.py
+stdenv.mkDerivation {
+  pname = "merge-after-ci";
+  version = "0.1.0";
+
+  src = ./.;
+
+  nativeBuildInputs = [ makeWrapper ];
+
+  buildInputs = [ python3 ];
+
+  installPhase = ''
+    runHook preInstall
+
+    mkdir -p $out/bin
+    cp merge-after-ci.py $out/bin/merge-after-ci
+    chmod +x $out/bin/merge-after-ci
+
+    wrapProgram $out/bin/merge-after-ci \
+      --prefix PATH : ${
+        lib.makeBinPath [
+          bash
+          coreutils
+          git
+          nix
+          openssh
+          tea
+          tea-create-pr
+          python3
+        ]
+      }
+
+    runHook postInstall
+  '';
+}