darwin.darling.src: fix build on case-sensitive filesystems

Co-authored-by: Andrew Childs <lorne@cons.org.nz>

pkgs/os-specific/darwin/darling/default.nix

@@ -8,11 +8,22 @@ stdenv.mkDerivation rec {
     url = "https://github.com/darlinghq/darling/archive/d2cc5fa748003aaa70ad4180fff0a9a85dc65e9b.tar.gz";
     sha256 = "11b51fw47nl505h63bgx5kqiyhf3glhp1q6jkpb6nqfislnzzkrf";
     postFetch = ''
-      # Get rid of case conflict
-      mkdir $out
+      # The archive contains both `src/opendirectory` and `src/OpenDirectory`,
+      # pre-create the directory to choose the canonical case on
+      # case-insensitive filesystems.
+      mkdir -p $out/src/OpenDirectory
+
       cd $out
       tar -xzf $downloadedFile --strip-components=1
       rm -r $out/src/libm
+
+      # If `src/opendirectory` and `src/OpenDirectory` refer to different
+      # things, then combine them into `src/OpenDirectory` to match the result
+      # on case-insensitive filesystems.
+      if [ "$(stat -c %i src/opendirectory)" != "$(stat -c %i src/OpenDirectory)" ]; then
+        mv src/opendirectory/* src/OpenDirectory/
+        rmdir src/opendirectory
+      fi
     '';
   };