Flush standard output after help is written (fix #4102)

(cherry picked from commit f5ac248b3ab9a70dc43ec8f8b9063aa200d94136)
Signed-off-by: Sébastien Escudier <sebastien-devel@celeos.eu>

src/libvlc.c

@@ -1303,6 +1303,7 @@ static void Help( libvlc_int_t *p_this, char const *psz_help_name )
 #ifdef WIN32        /* Pause the console because it's destroyed when we exit */
     PauseConsole();
 #endif
+    fflush( stdout );
 }
 
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