Its useful to be able to query a list of variables to obtain the values
in each multilib context. This adds such a function which works even
if called in the non-default recipe context.
(From OE-Core rev: 4202a09dece07c0d3f654c2b1ae504a031b4ee90)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>