We need this to ensure there are some correct values when building with
meta-darwin. This matches the addition of a common-mingw site file in
the core.
(From OE-Core rev: 8c2ade6f48dcc522c68f798286d1c43bd2c1c8e7)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>