Create a new class distutils-common-base.bbclass which holds the common
parts that can be used in native and target packages which need to use
distutils funtionality.
rpm, libxml2, zope are currently using them and needed to use
distutils-native-base for native recipes.
rpm and libxml need to defer the processing of certain configure
parameters which we evaluate using python. So we need to have python-native
built before we can process them. Hence we can not use EXTRA_OECONF
which is a python variable and gets expanded during parsing recipes
and ofcourse we have not yet built python-native.
We pass these extra options as a separate shell variable to do_configure
which we evaluate when that task is executing.