Fix -Wformat-security warnings

These warnings are kinda spammy, and they make sense in principle.
vlog_error takes a format string, so passing it an arbitrary string
(even error messages from libraries) isn't a good idea.

desktop_version/src/FileSystemUtils.cpp

@@ -306,7 +306,7 @@ static int setLevelDirError(const char* text, ...)
     retval = SDL_vsnprintf(levelDirError, sizeof(levelDirError), text, list);
     va_end(list);
 
-    vlog_error(levelDirError);
+    vlog_error("%s", levelDirError);
 
     return retval;
 }