There is no real point in adjusting overrides and creating a copy of the datastore,
just to access a single variable. We can do this just as easily with a slightly
more complicated getVar call. This improves performance.
(From OE-Core rev: 69f4351809359a0c7c38e8f233f3e3f7680ed2e2)
(From OE-Core rev: b5d65f5d5e5b26d3a2c673e899114c90bcaf6bc8)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>