ci(build): simplify Image.lz4 build rule insertion

Replace multi-line cat command with perl one-liner for cleaner Makefile modification

.github/workflows/build.yml

@@ -368,11 +368,7 @@ jobs:
             # Check if Image.lz4 build rule exists
             if ! grep -q "\$(obj)/Image.lz4: \$(obj)/Image FORCE" "$MAKEFILE_PATH"; then
               # Add the Image.lz4 build rule
-              cat >> "$MAKEFILE_PATH" << 'EOF'
-
-              $(obj)/Image.lz4: $(obj)/Image FORCE
-              $(call if_changed,lz4)
-              EOF
+              perl -pe 'print "\n\$(obj)/Image.lz4: \$(obj)/Image FORCE\n\$(call if_changed,lz4)\n" if eof' "$MAKEFILE_PATH" > "$MAKEFILE_PATH.tmp" && mv "$MAKEFILE_PATH.tmp" "$MAKEFILE_PATH"
             fi
           fi