Expand DISTRO_FEATURES and MACHINE_FEATURES fully so that any inner
variable references (such as DISTRO_FEATURES_LIBC) are expanded properly.
(From OE-Core rev: 01e372559052aa348ceced07540fdb774d292c65)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>