quickshell: build caelestia with clang

nixos/quickshell.nix

@@ -6,9 +6,35 @@ makeEnable config "myModules.quickshell" false {
       let
         hyprlandEnabled = lib.attrByPath ["myModules" "hyprland" "enable"] false nixos.config;
         system = pkgs.stdenv.hostPlatform.system;
+        quickshellBase = inputs.caelestia-shell.inputs.quickshell.packages.${system}.default.override {
+          # GCC 15.2 ICEs on generated NetworkManager DBus sources in
+          # quickshell 0.2.1. Quickshell's own dev shell uses clangStdenv.
+          stdenv = pkgs.clangStdenv;
+          withX11 = false;
+          withI3 = false;
+        };
+        quickshellUnwrapped = quickshellBase.unwrapped.overrideAttrs (old: {
+          # Clang then needs PCH disabled because quickshell's PipeWire target
+          # adds compile flags that do not match the shared PCH target.
+          cmakeFlags = (old.cmakeFlags or []) ++ [ (lib.cmakeBool "NO_PCH" true) ];
+        });
+        quickshellPackage = quickshellUnwrapped.stdenv.mkDerivation {
+          inherit (quickshellUnwrapped) version meta buildInputs;
+          pname = "${quickshellUnwrapped.pname}-wrapped";
+          nativeBuildInputs = quickshellUnwrapped.nativeBuildInputs ++ [ pkgs.qt6.wrapQtAppsHook ];
+          dontUnpack = true;
+          dontConfigure = true;
+          dontBuild = true;
+          installPhase = ''
+            mkdir -p $out
+            cp -r ${quickshellUnwrapped}/* $out
+          '';
+          passthru.unwrapped = quickshellUnwrapped;
+        };
         caelestiaPackage = inputs.caelestia-shell.packages.${system}.with-cli.override {
           # Caelestia pins app2unit 1.0.3, which no longer builds on this nixpkgs snapshot.
           app2unit = pkgs.app2unit;
+          quickshell = quickshellPackage;
         };
       in
       {