It seems like migrating to Qt6 is a win for multiple efforts, and I want us to evaluate switching to it as an alternative to monkey-patching Qt5/qmake to make it work properly.

1. First class support for Apple Silicon for Add macOS ARM build (universal or additional binaries) #20371 (see: https://bugreports.qt.io/browse/QTBUG-85279)
2. Transition from qmake to cmake (see: https://www.qt.io/blog/qt-6-build-system)
   1. We already use cmake in depends to build several other tools
   2. cmake is much better maintained than qmake
   3. This might make a native/build split possible for qt, the last holdout package of native/build mixing after boost was recently split
   4. For PRs like Depends : Qt Use Top-Level Structure #20600, where we're trying to work around qmake's jankiness, I don't want people to pour their heart and soul into making qmake work just to be completely replaced by cmake when we bump in the future

Supposedly, the switching cost is also minimal, as there's a Qt5Compat module (see: https://www.qt.io/blog/porting-from-qt-5-to-qt-6-using-qt5compat-library)