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>
(cherry picked from commit 5093435f66)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

utils/test-pkg

@@ -138,6 +138,8 @@ main() {
 
     printf "%d builds, %d skipped, %d build failed, %d legal-info failed\n" \
         ${nb} ${nb_skip} ${nb_fail} ${nb_legal}
+
+    return $((nb_fail + nb_legal))
 }
 
 build_one() {