chore: adapt to qt6xdg

[kegechen]

qt6xdg is comming..
https://github.com/lxqt/libqtxdg/releases/tag/4.0.0

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在CMakeLists.txt文件中，option命令的使用可能不正确，因为它应该在find_package之前使用。
• find_package命令的调用顺序似乎与find_package的文档说明不一致，应该检查是否需要调整以匹配文档中的顺序。
• if("${QT_VERSION_MAJOR}" STREQUAL "5")和elseif("${QT_VERSION_MAJOR}" STREQUAL "6")的条件判断可以简化，使用if语句直接比较字符串和数字。
• list(APPEND QT_LIBS Qt5::X11Extras)在CMakeLists.txt文件中调用，但在find_package之后，这可能会导致Qt5::X11Extras没有被正确地添加到QT_LIBS列表中。
• find_package(PkgConfig REQUIRED)之后没有调用pkg_check_modules，这可能会导致依赖项没有被正确地检查。
• if(ENABLE_QT_XDG_ICON_LOADER)条件判断之后，list(APPEND QT_LIBS ${QT_XDG_ICON_DEPS})应该在find_package之后调用，以确保所有必要的库都被正确地添加到QT_LIBS列表中。

是否建议立即修改:
是

[deepin-bot]

TAG Bot

New tag: 5.6.31
DISTRIBUTION: unstable
Suggest: synchronizing this PR through rebase #225

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: FeiWang1119, kegechen

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