Tool Chain Migration: objdump users, please test llvm-objdump

[Ed Maste]

Work is in progress to migrate fully to modern and permissively
licensed components for the tool chain. This includes moving away from
the three obsolete binutils components that are still in the base
system (as, ld, objdump). objdump is a tool to report information
about binary objects (such as headers, symbols, etc.), is not required
as a build tool, and in any case many uses of objdump are better
served by readelf.

For FreeBSD 12 I intend to remove GNU objdump 2.17.50. PR 229046[1] is
open to track tasks related to its removal, and users who need GNU
objdump can install an up-to-date version from the ports tree or the
binutils package.

That said, llvm includes a somewhat equivalent llvm-objdump, and it is
built by default in FreeBSD now. If llvm-objdump's command line option
support and output format is "close enough" to GNU objdump for most
users we may decide to install it as /usr/bin/objdump. Therefore, I
would like to ask users of GNU objdump in FreeBSD to give llvm-objdump
a try. Please let me know if it works for your uses, or describe
deficiencies that you found.

[1] https://bugs.freebsd.org/229046