For the meta-mingw layer, we need to process alternative SDK_OS, since this
is not a Linux based OS.
(From OE-Core rev: b31e015d2e379c24610948d345c5970545887468)
Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>