QmlDebugger: Cannot debug on systems with journald support

Steps to reproduce:

• have a Qt built with journald support
• build QC with CONFIG+=journald with this Qt
• start QC, create Quick Application from template, using this Qt
• place a bp into the main.cpp and into the main.qml
• start debugging
  • bp inside the main.cpp is hit -> trigger continue

Current result:

• nothing else happens, debugger log prints (almost continuously) 'Cannot connect to QML debugger'
• when using 'journalctl -f' on the cmdline you'll see that the respective messages (port where it listens) of the qmldebugger are printed to the journal (I guess that QC tries to get the messages from stdout/stderr?)

Note: Using a 'normal' (official release without journald support) Qt works fine.
Note: Disabling C++ debugging for this project seems to work fine then, except for when hitting a bp, the debugging session finishes after a split of a second - but this seems to be related to using Qt5.5.0. (using Qt5.4.0 stops fine at bp when disabling C++ debugging)