Debug stepping is not reliable on QNX

Steps to reproduce

1. Install Qt from Qt 5.12.0 RC offline installer for QNX7
2. Set up example "trafficlight-qml-simple"
3. Set breakpoint to trafficlight-qml-simple.cpp to line
   • "engine.load(QUrl(QStringLiteral("qrc:/TrafficLight.qml")));"
4. Start debugging
5. When debugging breaks, press "step over"

Expected outcome

• gdb breaks on next line

Actual outcome

• gdb breaks again for the same line, but does not break to the next
• Pressing "step over" again does not help

Workaround

• Insert another breakpoint to the next line
• Press "continue gdb"