python-distutilscross: remove package that is no longer needed

Thanks to the previous commit that makes distutilscross unecessary for
setuptools packages, the host-distutilscross package can now be
removed. There is no need for any Config.in.legacy handling, since
there is no target variant, or visible Config.in option for
host-distutilscross.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>