Disable logging at exit on FreeBSD.

This commit fixes a crash on KiCad exit for FreeBSD.

Usage of the wxLog functions in destructors on program generates an
infinite recursive call loop and segfault on this platform.

The workaround is inpired by:
  https://people.freebsd.org/~wpaul/kicad/kicad_instructions.txt

Fixes: lp:1778334
* https://bugs.launchpad.net/kicad/+bug/1778334

kicad/kicad.cpp

@@ -241,6 +241,11 @@ struct APP_KICAD : public wxApp
     {
         program.OnPgmExit();
 
+#if defined(__FreeBSD__)
+        /* Avoid wxLog crashing when used in destructors. */
+        wxLog::EnableLogging( false );
+#endif
+
         return wxApp::OnExit();
     }