scripts: coccicheck: Improve error feedback when coccicheck fails

Currently, coccicheck fails with only the message "coccicheck failed"
and the error code for the failure. To obtain the error logs,
one needs to specify a debug file using the DEBUG_FILE option.

Modify coccicheck to display error logs when it crashes unless
DEBUG_FILE is set, in which case, the error logs are stored in
the specified debug file.

Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>