There's a sort-of-official port of asciidoc to Python 3. Whilst the official
replacement is asciidoctor which is rewritten in Ruby, this is a fairly trivial
swap and removes Python 2 from core-image-sato builds entirely.
Moving forward we should evaluate asciidoctor, but that can wait.
Change the RDEPENDS so that python3 is only a dependency for target and
nativesdk builds, for native this can use the host python3.
Remove redundant DESTDIR export that isn't needed.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
