* Adding nlopt package (WIP)
* cxxflags added, nlopt builds
* Add docs and test for cxxflags feature
* Applied black formatter
* Remove nlopt new pkg from this branch
* Removed empty cxxflags option from SciPy meta.yaml
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.
Modified ``Makefile`` and ``packages/Makefile`` to get ``PYODIDE_PACKAGE_ABI`` from ``Makefile.envs``
Made ``checkABI`` as a public API function.
Modified ``file_packager.py`` to check for the compatible ABI number.
Defined ABI number with which pyodide is built in Makefile.envs
Accepted ABI number in ``file_packager.py`` as an argument.
Modified ``buildpkg.py`` and ``buildall.py`` to account for the new argument.
Added the corresponding ``test_different_ABI`` test.