sync.stdatomic: workaround libatomic.a indirect symbols tcc bug

[kbkpbot]

Fix issue #23924

This is due to a tcc bug handling indirect(IFUNC) symbols in .a.
I think it should generate a GOT/PLT in output elf file.
It can't determine the symbol's address at compile time.
https://lists.nongnu.org/archive/html/tinycc-devel/2025-05/msg00010.html

$ uname -a
Linux armbian 5.15.49-flippy-74+o #134 SMP PREEMPT Wed Jun 22 22:05:04 CST 2022 aarch64 aarch64 aarch64 GNU/Linux

$ nm libatomic.a | grep __atomic_fetch_add
nm: init.o：无符号
0000000000000050 i __atomic_fetch_add_1
0000000000000050 i __atomic_fetch_add_2
0000000000000050 i __atomic_fetch_add_4
0000000000000050 i __atomic_fetch_add_8
00000000000000b0 i __atomic_fetch_add_16

The i show above mean IFUNC(indrect) symbol.

$ uname -a
Linux mars-QiTianM428-A688 6.8.0-59-generic #61-Ubuntu SMP PREEMPT_DYNAMIC Fri Apr 11 23:16:11 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

$ nm libatomic.a | grep __atomic_fetch_add
0000000000000000 T __atomic_fetch_add_1
0000000000000000 T __atomic_fetch_add_2
0000000000000000 T __atomic_fetch_add_4
0000000000000000 T __atomic_fetch_add_8
0000000000000090 i __atomic_fetch_add_16

[huly-for-github]

Connected to Huly®: V_0.6-22841

[spytheman]

Excellent work.