rootfs.py: Make set -x not break rootfs creation
The rootfs logfile check errors out if it finds an "exit 1" in
a log. But consider the shell idiom:
if ! $command; then exit 1; fi
and consider a postinstall script with a "set -x" for debugging
purposes (to get log output in /var/log/postinstall.log.)
Solution: Ignore lines prefixed with a +, because those show shell
code even if a specific fragment won't be executed.
(From OE-Core rev:
f23f129dba66144abf8fe8450320e01fa4c02f5c)
Signed-off-by: Peter Seebach <peter.seebach@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
