link_elf_obj: Process init_array and fini_array

[markj]

Summary

Reuse the existing logic for .ctors/.dtors.

This is required for KASAN.

[markj]

sys/kern/link_elf_obj.c

535

I am not sure why .dtors is not handled. I don't have a use for it but can implement it if it seems worthwhile.

[kib]

In principle it could be that an object contains both .ctors and SHT_INIT_ARRAY sections. I suggest to warn, at least.

BTW, we rely on ld -r correctly merge all sections with the same name+attributes, but for many reasons this might not occur. So I think a warning is due if ctors_addr is non-NULL.

[markj]

Print a warning if ctors_addr is already non-zero.