Continuous integration on ARM64 and PPC64le

[kif]

There is a prototype in fabio: https://github.com/silx-kit/fabio/pull/341

What we learnt: There are no binary wheels of h5py which is hence built from scratch. This requires the lib HDF5 and its development packages to be installed on the system using apt-get. More-over the auto-dicovery tool from h5py does not work unless one provides an environment variable HDF5_PATH=/usr/lib/powerpc64/hdf5.

Silx having an extra dependency on Qt, there are probably also some glitches there to be expected.

[vallsv]

BTW, you can skip Qt on tests

[vallsv]

It was also possible to skip h5py a long time ago. I dont think it is anymore possible.

[kif]

No more possible