Debugger: Suppress gdb warnings regarding controlling terminal
Debugger: Suppress gdb warnings regarding controlling terminal

Causes more confusion for users than actual trouble. A hint is
still left in the debugger log, so it's not completely gone.

Task-number: QTCREATORBUG-3918
Change-Id: I51244094811bcb5c436f0631cb02dbf41cc202bf
Reviewed-by: Christian Stenger <accbb51712d7b9c4fb108439d01e716148e5f9e6@theqtcompany.com>

Distrotech/qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,Distrotech/qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,danimo/qt-creator,danimo/qt-creator,xianian/qt-creator,Distrotech/qtcreator,danimo/qt-creator,danimo/qt-creator,Distrotech/qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,xianian/qt-creator,danimo/qt-creator,Distrotech/qtcreator,Distrotech/qtcreator,xianian/qt-creator,Distrotech/qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator