wifi: cfg80211: sort certificates in build

The build can become unreproducible if the list of files
found by $(wildcard ...) differs. Sort the list to avoid
this.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/Makefile

@@ -25,7 +25,7 @@ ifneq ($(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR),)
 cfg80211-y += extra-certs.o
 endif
 
-$(obj)/shipped-certs.c: $(wildcard $(srctree)/$(src)/certs/*.hex)
+$(obj)/shipped-certs.c: $(sort $(wildcard $(srctree)/$(src)/certs/*.hex))
 	@$(kecho) "  GEN     $@"
 	$(Q)(echo '#include "reg.h"'; \
 	  echo 'const u8 shipped_regdb_certs[] = {'; \
@@ -35,7 +35,7 @@ $(obj)/shipped-certs.c: $(wildcard $(srctree)/$(src)/certs/*.hex)
 	 ) > $@
 
 $(obj)/extra-certs.c: $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR) \
-		      $(wildcard $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR)/*.x509)
+		      $(sort $(wildcard $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR)/*.x509))
 	@$(kecho) "  GEN     $@"
 	$(Q)(set -e; \
 	  allf=""; \