We can't use subprocess.check_output() or subprocess.call() here since the one
who invokes runcmd() needs handle CmdError() exception (error out or ignore
it).
(From OE-Core rev: c3e7739987d804f7865428442479d5bece5ff2dd)
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>