This is needed for the upstream backend, and I believe is a noop under
the fastcomp backend
Co-authored-by: Michael Droettboom <mdboom@gmail.com>
Co-authored-by: Joe Marshall <joe.marshall@nottingham.ac.uk>
This addresses part of #713, by listing and building C libraries as
dependencies. This means we automatically build CLAPACK when needed, and
`lxml`'s C dependencies are not built if lxml is not. In particular,
building "core" should now be faster.
The building itself is still performed by Makefile.
Roman Yurchak