Use a set of ELF Tool Chain tools by default

These tools are now from the ELF Tool Chain project:

• addr2line
• elfcopy (strip)
• nm
• size
• strings

The binutils versions are available by setting in src.conf:
WITHOUT_ELFTOOLCHAIN_TOOLS=yes

Thanks to antoine@ for multiple exp-runs and diagnosing many of the
failures.

PR: 195561 (ports exp-run)
Sponsored by: The FreeBSD Foundation