qt6: move mkspecs/modules to dev output

pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh

@@ -54,9 +54,12 @@ else # Only set up Qt once.
         dontPatchMkspecs=1
 
         local lib="${!outputLib}"
+        local dev="${!outputDev}"
 
-        if [ -d "$lib/mkspecs/modules" ]; then
-            fixQtModulePaths "$lib/mkspecs/modules"
+        moveToOutput "mkspecs/modules" "$dev"
+
+        if [ -d "$dev/mkspecs/modules" ]; then
+            fixQtModulePaths "$dev/mkspecs/modules"
         fi
 
         if [ -d "$lib/mkspecs" ]; then

pkgs/development/libraries/qt-6/modules/qtbase.nix

@@ -244,7 +244,8 @@ stdenv.mkDerivation rec {
   moveToDev = false;
 
   postFixup = ''
-    fixQtModulePaths  "$out/mkspecs/modules"
+    moveToOutput      "mkspecs/modules" "$dev"
+    fixQtModulePaths  "$dev/mkspecs/modules"
     fixQtBuiltinPaths "$out" '*.pr?'
   '';