[bug#28690] provide a lib output for boost

[Dave Love <dave.love@manchester.ac.uk>]

Thomas Danckaert <post@thomasdanckaert.be> writes:

> I don't think it's possible to have one output of a package depend on
> another, though.  We could just add boost:lib to the inputs for every
> package which relies on boost (except for packages which only rely on
> header-only parts of boost)?

Sorry, I don't understand; the usual problem seems to be _preventing_
that, e.g. to cure cycles.  It may not be in the package definition, but
if I mention "lib" in some file in "out", it will do the job, won't it?

> Another solution might be to turn the 2 outputs into 2 separate guix
> packages, "boost" and "boost-libs", where "boost" only contains the
> headers, and has "boost-libs" as a propagated-input.  I'm not sure if
> this will do the right thing (i.e. make boost-libs available in the
> build environment when boost is a regular input, but not propagate it
> further), someone should try it out ;).
>
> Thomas

I don't think that's necessary, but the fact that this sort of thing
isn't straightforward seems to me a Guix deficiency which might be
addressed.