Redirect stderr to stdout when running subcommands while doing the SDK
tests. The tests will show stdout when CalledProcessError is raised,
but any output to stderr was lost.
(From OE-Core rev: 7cb4e9ab8c1596281060e94a216966060103956e)
Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>