When assigning symbol version, we should hide debug symbols defined in
discarded sections from IR objects so that they can be removed later.
bfd/
PR ld/23818
* elflink.c (_bfd_elf_link_assign_sym_version): Hide symbols
defined in discarded input sections.
ld/
PR ld/23818
* testsuite/ld-plugin/lto.exp: Run PR ld/23818 test.
* testsuite/ld-plugin/pr23818.d: New file.
* testsuite/ld-plugin/pr23818.t: Likewise.
* testsuite/ld-plugin/pr23818a.c: Likewise.
* testsuite/ld-plugin/pr23818b.c: Likewise.
