gen,os: fix tcc __attribute__, fix os.notify

[kbkpbot]

This is a extend of PR #25779

According to
https://github.com/TinyCC/tinycc/blob/7e4fc3a0d01173575b3b29f71ae4da87322ba14b/tcc.h#L28-L35

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
/* gnu headers use to #define __attribute__ to empty for non-gcc compilers */
#ifdef __TINYC__
# undef __attribute__
#endif

and a discussion at https://lists.nongnu.org/archive/html/tinycc-devel/2025-10/msg00006.html

It need to fix the header for tcc work with __attribute__.

[spytheman]

Excellent work.
Thanks for investigating @kbkpbot 🙇🏻 .