GitLab

Add libtool, flex, and bison.

flex must be fetched from the released archive, rather
than the GitHub autogenerated source.

Fetch OpenBLAS from wheels.scipy.org rather than building it.

* Revert "Revert "[osx_steps] export cppflags""

This reverts commit 7956064f.

* Try using LIBRARY_PATH instead of LDFLAGS

This reverts commit 4f303070.

Prefer multibuild library locations over the defaults.
Sometimes multibuild would use an older version
over it's own.

* [library_builders] use brew to install openblas

Yields better performance on OSX

* [tst:library_builders] add openblas

* [tst:library_builders] update homebrew

* fix bash

* [library_builders] force openblas link

* ENH: libraries: add a build_github function

* FIX: use name stamp

* MAINT: remove noop

* [tst:library_builders] add build_github