When a global symbol is defined in COMDAT group, we shouldn't leave an
undefined symbol in symbol table when the symbol section is discarded
unless there is a reference to the symbol outside of COMDAT group.
bfd/
PR ld/17550
* elf-bfd.h (elf_link_hash_entry): Update comments for indx,
documenting that indx == -3 if symbol is defined in a discarded
section.
* elflink.c (elf_link_add_object_symbols): Set indx to -3 if
symbol is defined in a discarded section.
(elf_link_output_extsym): Strip a global symbol defined in a
discarded section.
ld/
PR ld/17550
* testsuite/ld-elf/pr17550-1.s: New file.
* testsuite/ld-elf/pr17550-2.s: Likewise.
* testsuite/ld-elf/pr17550-3.s: Likewise.
* testsuite/ld-elf/pr17550-4.s: Likewise.
* testsuite/ld-elf/pr17550a.d: Likewise.
* testsuite/ld-elf/pr17550b.d: Likewise.
* testsuite/ld-elf/pr17550c.d: Likewise.
* testsuite/ld-elf/pr17550d.d: Likewise.
