Debugger: Trim ABI list for GDB based debuggers

Do not end up appending to the existing list of ABIs when reinitializing
GDB debuggers.

Task-number: QTCREATORBUG-10642
Change-Id: Ic023f1fa269dbc05c0a44c3acf2cc8dd22f0565c
Reviewed-by: Christian Stenger <christian.stenger@digia.com>

src/plugins/debugger/debuggeritem.cpp

@@ -98,6 +98,7 @@ void DebuggerItem::reinitializeFromFile()
         m_engineType = NoEngineType;
         return;
     }
+    m_abis.clear();
     QByteArray ba = proc.readAll();
     if (ba.contains("gdb")) {
         m_engineType = GdbEngineType;