PR 22319
bfd * elflink.c (elf_link_output_extsym): Keep global undefined
symbols if they have been marked as needed.
ld * testsuite/ld-elf/pr22310.s: New test source file.
* testsuite/ld-elf/pr22310.d: New test driver.
* testsuite/ld-mmix/undef-3.d: Update expected output from readelf.