QML debugging is really slow on an embedded device

Steps to reproduce:

1. Install any b2qt binary (Qt 5.15.4) and 4.15.0 Qt Creator (from staging)
2. Open QtC and create a new Qt Quick (Empty) application (qmake based)
3. Set a breakpoint to main.qml (line 84 onActiveChanged)
4. Build and start debugger

Expected result:

Debugger stops to the breakpoint

Actual result:

Starting debugger takes a really long time and a dialog asking "Give GDB more time" is shown. After giving GDB more time few times, debugger stops to the QML breakpoint. This is reproducible on all supported embedded devices.