Debugger: Use Startparameters.debuggerCommand for command.

Use in both engines preferred over ABI if it is compatible.
Report start parameters. Introduce gdb configuration check.

src/plugins/debugger/gdb/gdbengine.h

@@ -132,7 +132,6 @@ private: ////////// Gdb Process Management //////////
 
     AbstractGdbAdapter *createAdapter();
     bool startGdb(const QStringList &args = QStringList(),
-                  const QString &gdb = QString(),
                   const QString &settingsIdHint = QString());
     void handleInferiorShutdown(const GdbResponse &response);
     void handleGdbExit(const GdbResponse &response);