Fix GCC compiler warning

src/GAudioOutput.cc

@@ -97,7 +97,11 @@ GAudioOutput::GAudioOutput(QObject *parent) : QObject(parent),
 
 #if defined Q_OS_LINUX && defined QGC_SPEECH_ENABLED
     espeak_Initialize(AUDIO_OUTPUT_PLAYBACK, 500, NULL, 0); // initialize for playback with 500ms buffer and no options (see speak_lib.h)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
+    // Even though the following is legal, GCC still complains about it
     espeak_VOICE espeak_voice = {};
+#pragma GCC diagnostic pop
     espeak_voice.languages = "en-uk"; // Default to British English
     espeak_voice.name = "klatt"; // espeak voice name
     espeak_voice.gender = 2; // Female