utils/test-pkg: ensure to exit with an error upon failure
This commit modifies the main() function so that it returns the sum of
build and legal errors, making sure the overall test-pkg script exists
with a non-zero error code upon failure.
Signed-off-by: Heiko Thiery <heiko.thiery@kontron.com>
[Thomas: improved commit log]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>