fix: use dontUseCmakeInstall + stub for qtquick3d cross-compile

flake.nix

@@ -82,13 +82,12 @@
           '';
         });
         emacs-pgtk = prev.emacs-pgtk.override { withMailutils = false; };
-        # qtquick3d: Qt::Quick not available in aarch64 cross-compile qtdeclarative
-        # Make it a no-op so qtmultimedia / wireshark / js8call still build
+        # qtquick3d: Qt::Quick not in aarch64 cross-compile qtdeclarative
+        # cmake skips building when Qt::Quick missing, then install fails
         qtquick3d = prev.qtquick3d.overrideAttrs (old: {
+          dontUseCmakeInstall = true;
           installPhase = ''
-            runHook preInstall
-            cmake --install . --prefix "$out" 2>/dev/null || mkdir -p "$out"
-            runHook postInstall
+            mkdir -p "$out"
           '';
         });
         # perl-ldap fails cross-compile (Module::Install needs dynamic loading)