difftastic: patch bundled mimalloc source to build on older macos

same patch as introduced to our own mimalloc in
9ba8bda313

pkgs/tools/text/difftastic/default.nix

@@ -1,4 +1,11 @@
-{ lib, fetchFromGitHub, rustPlatform, tree-sitter, difftastic, testers }:
+{ lib
+, fetchFromGitHub
+, fetchpatch
+, rustPlatform
+, tree-sitter
+, difftastic
+, testers
+}:
 
 rustPlatform.buildRustPackage rec {
   pname = "difftastic";
@@ -11,7 +18,29 @@ rustPlatform.buildRustPackage rec {
     sha256 = "sha256-jdkyDsuOOG1dJmgRmMp2KhY9ermccjrxK2JAIzpO6nw=";
   };
 
-  cargoSha256 = "sha256-qHG3ve8HoMWBS/x6mRbXMsrpcqNqfVcbAkfYOk7Su/0=";
+  depsExtraArgs = {
+    postBuild = let
+      mimallocPatch = (fetchpatch {
+        name = "mimalloc-older-macos-fixes.patch";
+        url = "https://github.com/microsoft/mimalloc/commit/40e0507a5959ee218f308d33aec212c3ebeef3bb.patch";
+        stripLen = 1;
+        extraPrefix = "libmimalloc-sys/c_src/mimalloc/";
+        sha256 = "1cqgay6ayzxsj8v1dy8405kwd8av34m4bjc84iyg9r52amlijbg4";
+      });
+    in ''
+      pushd $name
+      patch -p1 < ${mimallocPatch}
+      substituteInPlace libmimalloc-sys/.cargo-checksum.json \
+        --replace \
+          '6a2e9f0db0d3de160f9f15ddc8a870dbc42bba724f19f1e69b8c4952cb36821a' \
+          '201ab8874d9ba863406e084888e492b785a7edae00a222f395c079028d21a89a' \
+        --replace \
+          'a87a27e8432a63e5de25703ff5025588afd458e3a573e51b3c3dee2281bff0d4' \
+          'ab98a2da81d2145003a9cba7b7025efbd2c7b37c7a23c058c150705a3ec39298'
+      popd
+    '';
+  };
+  cargoSha256 = "12a12ng9wz2rrj3xzhgrqlg3lxpqxwdgvkz3fxny17nysmmpnhvv";
 
   passthru.tests.version = testers.testVersion { package = difftastic; };