update_headers.sh: Cleanly report failure on error

If in intermediate step fails, update_headers.sh blindly continues
and may return success status.

To avoid errors going unnoticed when driving this script, exit and
report failure status as soon as something goes wrong.  For good
measure, also fail on expansion of undefined shell variables to aid
future maintainers.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
1 file changed