Fixed empty line handling process_config.sh

This commit fixed empty line handling in the config file for being able to used KConfig-based defconfigs with the empty lines in them

tools/process_config.sh

@@ -56,9 +56,15 @@ process_file() {
                 exit 1
             fi
         else
-            local key_config="$(echo "$line" | cut -d= -f1)="
-            sed -i.backup "/$key_config/d" $output_file
-            echo "$line" >> $output_file
+            if [[ -n "$line" ]]; then
+                local key_config="$(echo "$line" | cut -d= -f1)="
+                sed -i.backup "/^$key_config/d" "$output_file"
+                echo "$line" >> "$output_file"
+
+                echo "Appended $line to $output_file"
+            else
+                echo "The empty line from defconfig was skipped from adding to $output_file"
+            fi
         fi
     done < "$input_file"
 }