macos : fix “sed: -I or -i may not be used with stdin”

tools/Unix.mk
added $(call DELFILE, .config.backup)

tools/process-config.sh
sed-i -> sed -i.backup

tools/Unix.mk

@@ -799,6 +799,7 @@ endif
 	$(call DELFILE, .config)
 	$(call DELFILE, .config.old)
 	$(call DELFILE, .config.orig)
+	$(call DELFILE, .config.backup)
 	$(call DELFILE, .gdbinit)
 
 # Application housekeeping targets.  The APPDIR variable refers to the user

tools/process_config.sh

@@ -57,7 +57,7 @@ process_file() {
             fi
         else
             local key_config="$(echo "$line" | cut -d= -f1)="
-            sed -i "/$key_config/d" $output_file
+            sed -i.backup "/$key_config/d" $output_file
             echo "$line" >> $output_file
         fi
     done < "$input_file"