cannot copy file libqt6ct.so

[milahu]

this is on nixos, where qtbase is read only

-- Installing: /nix/store/wzms2f5b1014knb4dl72s66rmk3d2401-qtbase-6.2.2-bin/lib/qt-6.2.2/plugins/platformthemes/libqt6ct.so
CMake Error at src/qt6ct-qtplugin/cmake_install.cmake:60 (file):
  file INSTALL cannot copy file
  "/build/source/build/src/qt6ct-qtplugin/libqt6ct.so" to
  "/nix/store/wzms2f5b1014knb4dl72s66rmk3d2401-qtbase-6.2.2-bin/lib/qt-6.2.2/plugins/platformthemes/libqt6ct.so":
  Permission denied.
Call Stack (most recent call first):
  cmake_install.cmake:52 (include)


make: *** [Makefile:100: install] Error 1

fix: allow to set PLUGINDIR with cmake -DPLUGINDIR=/some/where/else also qt5ct allows to set PLUGINDIR

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,8 +39,10 @@
     message(FATAL_ERROR "Could NOT find lrelease executable")
 endif()
 
-#execute_process(COMMAND ${QT_QTPATHS_EXECUTABLE} -query QT_INSTALL_PLUGINS OUTPUT_VARIABLE PLUGINDIR OUTPUT_STRIP_TRAILING_WHITESPACE)
-execute_process(COMMAND ${QT_QTPATHS_EXECUTABLE} --plugin-dir OUTPUT_VARIABLE PLUGINDIR OUTPUT_STRIP_TRAILING_WHITESPACE)
+if(NOT DEFINED PLUGINDIR)
+    #execute_process(COMMAND ${QT_QTPATHS_EXECUTABLE} -query QT_INSTALL_PLUGINS OUTPUT_VARIABLE PLUGINDIR OUTPUT_STRIP_TRAILING_WHITESPACE)
+    execute_process(COMMAND ${QT_QTPATHS_EXECUTABLE} --plugin-dir OUTPUT_VARIABLE PLUGINDIR OUTPUT_STRIP_TRAILING_WHITESPACE)
+endif()
 message(STATUS "Plugin path: " ${PLUGINDIR})
 
 message(STATUS "Generating translations ...")