On most distros, these are just built and distributed as part of
binutils. We don't use binutils across the board, however, but rather
switch between binutils and a cctools-binutils mashup, and change the
outputs on binutils too. This creates a combinatorial conditional soup
which is hard to maintain.

My hope is to lower the the state space. While my patch isn't the most
maintainable, they make downstream packages become more maintainable to
compensate. The additional derivations themselves are completely
platform-agnostic, always they always supports all possible target
platforms, and always yield "out" and "dev" outputs. That, in turn,
allows downstream packages to not worry about a dependency
shape-shifting under them.

In fact, the actual binutils package can avoid needing multiple outputs
now that these serve the requisite libraries, so that also can become
simpler on all platforms, too, removing the original wart this PR
circumnavigates for now. Actually changing the binutils package to
leverage is a mass rebuild, however, so I'll leave that for a separate
PR.

I do hope to upstream something like my patch too, but until then I'll
make myself maintainer of these derivations

  - Use nativeBuildInputs
  - Use libraries opcodes and bfd, rather than all of binutils

One should depend on

 - `stdenv.cc.bintools`: for executables at build time
 - `libbfd` or `libiberty`: for those libraries
 - `targetPackages.cc.bintools`: for exectuables at *run* time
 - `binutils`: only for specifically GNU Binutils's executables, regardless of
   the host platform, at run time.

There are separate derivations for these libraries and we don't want
conflict. Multitarget is generally more useful, and will eventually
speed up cross builds, so why not?!

bfd, opcodes: Init separate derivations for binutils libraries