introduce minifakeroot that also works on macos

nixosModules/clanCore/zerotier/default.nix

@@ -182,15 +182,33 @@ in
         secret.zerotier-identity-secret = { };
         generator.path = [
           config.services.zerotierone.package
-          pkgs.fakeroot
           pkgs.python3
         ];
-        generator.script = ''
-          python3 ${./generate.py} --mode network \
-            --ip "$facts/zerotier-ip" \
-            --identity-secret "$secrets/zerotier-identity-secret" \
-            --network-id "$facts/zerotier-network-id"
-        '';
+        generator.script =
+          let
+            library = "libfakeroot${pkgs.stdenv.hostPlatform.extensions.sharedLibrary}";
+            minifakeroot = pkgs.stdenv.mkDerivation {
+              name = "minifakeroot";
+              dontUnpack = true;
+              installPhase = ''
+                mkdir -p $out/lib
+                ${
+                  if pkgs.stdenv.isDarwin then
+                    "$CC -dynamiclib -o $out/lib/libfakeroot.dylib ${./fake_root.c}"
+                  else
+                    "$CC -shared -o $out/lib/libfakeroot.so ${./fake_root.c}"
+                }
+              '';
+            };
+            varName = if pkgs.stdenv.isDarwin then "DYLD_INSERT_LIBRARIES" else "LD_PRELOAD";
+          in
+          ''
+            export ${varName}=${minifakeroot}/lib/${library}
+            python3 ${./generate.py} --mode network \
+              --ip "$facts/zerotier-ip" \
+              --identity-secret "$secrets/zerotier-identity-secret" \
+              --network-id "$facts/zerotier-network-id"
+          '';
       };
       clan.core.state.zerotier.folders = [ "/var/lib/zerotier-one" ];