Also use --no-keyring for expiry check. Prevents redundant keybox creation.

Makefile

@@ -16,11 +16,11 @@ keyrings/gnupg:
 	install -m700 -d $@
 
 define import-keys =
-	cat $^ | gpg $(GPG_OPTIONS) --no-keyring --import-options import-export --import > $@
+	cat $^ | gpg --no-keyring --import-options import-export --import > $@
 endef
 
 define check-expiry =
-	for k in $$(gpg --with-colons --fixed-list-mode --show-keys $@ | grep -e '^pub' -e '^sub'); do \
+	for k in $$(gpg --no-keyring --with-colons --fixed-list-mode --show-keys $@ | grep -e '^pub' -e '^sub'); do \
 	    expiry=$$(echo $$k | cut -d: -f7) ; \
 	    if [ -n "$${expiry}" ] && [ $${expiry} -lt $(EXPIRY_CHECK) ] ; then \
 	        echo ERROR: $$(echo $$k | cut -d: -f5) expires too soon: $$(date -d@$${expiry}) ; \