python-from-host: use HOST_PYTHON to get Python install dir

[johannesring]

This will fix #882.

[johannesring]

The test test.host-scipy.yaml is failing because HOST_PYTHON is not set in suse.yaml. We can either fix this by setting HOST_PYTHON in suse.yaml or extending from debian.yaml instead of suse.yaml in test.host-scipy.yaml. Maybe we should do both?

[cekees]

My vote would be just to put it in suse.yaml and not extend from debian.yaml. I could be wrong, but I thought the idea was to loosely mirror the ancestry of the linux distributions with these basic profiles like suse.yaml and debian.yaml, and I don't think suse descends from debian.

[johannesring]

Thanks for your comment. I have added HOST_PYTHON now in suse.yaml.

[johannesring]

Should we add HOST_PYTHON in the other basic profiles like centos.yaml, darwin.yaml, homebrew.yaml, linux.yaml, osx_clt.yaml and osx.yaml? It has already been set in arch.yaml, cygwin.yaml, debian.yaml and macports.yaml.