Fix build with Qt6.10

https://bugs.gentoo.org/966288

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -609,6 +609,10 @@ ELSE()
 ENDIF()
 FIND_PACKAGE(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS
      Concurrent Gui Network Widgets Charts Positioning)
+SET(USE_BUNDLED_QTCOMPRESS 1 CACHE BOOL "Use bundled version of qtcompress")
+IF(Qt6_VERSION VERSION_GREATER_EQUAL 6.10 AND NOT USE_BUNDLED_QTCOMPRESS)
+     FIND_PACKAGE(Qt6 REQUIRED COMPONENTS GuiPrivate)
+ENDIF()
 IF(USE_PLUGIN_TELESCOPECONTROL OR ENABLE_GPS)
      FIND_PACKAGE(Qt${QT_VERSION_MAJOR} COMPONENTS SerialPort REQUIRED)
 ENDIF()
@@ -809,7 +813,6 @@ ELSE()
      MESSAGE(STATUS "Using system-provided zlib at ${ZLIB_LIBRARIES}")
 ENDIF()
 
-SET(USE_BUNDLED_QTCOMPRESS 1 CACHE BOOL "Use bundled version of qtcompress")
 IF(USE_BUNDLED_QTCOMPRESS)
      ADD_DEFINITIONS(-DUSE_BUNDLED_QTCOMPRESS)
      MESSAGE(STATUS "Using bundled qtcompress at ${CMAKE_SOURCE_DIR}/src/external/qtcompress")