buildcheck: reduce DEBUG_INFO noise from reference* scripts

From: Randy Dunlap <rddunlap@osdl.org>

Reduce noise in 'make buildcheck' that is caused by CONFIG_DEBUG_INFO=y.

Signed-off-by: Randy Dunlap <rddunlap@osdl.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>