Call for testing: elftoolchain tools

[Ed Maste]

We have a rather outdated version of binutils in the base system.  As
part of a project to update our toolchain I've started working on
using some of the tools from the elftoolchain project.  There is now a
build knob to enable the use of the following tools:

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

The knob (in /etc/src.conf) is:
WITH_ELFTOOLCHAIN_TOOLS=yes

The binutils version is still used for as, ld, objcopy, objdump and
readelf; future projects will handle these.

The option is being tested in ports exp-runs on amd64 and i386, and
has had basic sanity testing on arm64 and mips64.

I'm interested in test reports across a variety of hardware
architectures and use cases.  If everything works as expected you
should see no difference -- the tools should be drop-in replacements.

-Ed