None of the Python invocations that this changes are actually called, and
there's no need to provide a HOSTPGEN variable when the recipe can just override
PGEN directly.
(From OE-Core rev: 47a8602171428b7ce5d897f7e2c2f26b203b8b63)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>