The idea of squashing packagegroup dependencies was to avoid allarch
packages rebuilding upon tune/arch changes. Now that the allarch class
inclusion is conditional, we can narrow down the packagegroup squashing
to be specifically applied to allarch recipes.
(From OE-Core rev: bd8018792155ae842952432900c8431feeaffe30)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>