dd comment and set eip unused

Former-commit-id: 685b87e2ef4f67cd599b12e38b08f5b70b7a6c58

src/debug.cpp

@@ -1610,7 +1610,8 @@ void safe_write(int fd, const void *pv, ssize_t cb)
  * The eip argument is unused as libunwind only gets local context.
  * The uplevel argument indicates how many of the calling functions to skip.
  */
-void logStackTrace(UNUSED void * eip, int uplevel) {
+void logStackTrace(void * eip, int uplevel) {
+    (void)eip;//UNUSED
     int fd = openDirectLogFiledes();
 
     if (fd == -1) return; /* If we can't log there is anything to do. */