helix: prevent grammars referencing sources (#233580)

        then "${source}/${grammar.source.subpath}"

        else source;

      dontUnpack = true;

      dontConfigure = true;

      FLAGS = [

      buildPhase = ''

        runHook preBuild

        if [[ -e "$src/src/scanner.cc" ]]; then

          $CXX -c "$src/src/scanner.cc" -o scanner.o $FLAGS

        elif [[ -e "$src/src/scanner.c" ]]; then

          $CC -c "$src/src/scanner.c" -o scanner.o $FLAGS

        if [[ -e "src/scanner.cc" ]]; then

          $CXX -c "src/scanner.cc" -o scanner.o $FLAGS

        elif [[ -e "src/scanner.c" ]]; then

          $CC -c "src/scanner.c" -o scanner.o $FLAGS

        fi

        $CC -c "$src/src/parser.c" -o parser.o $FLAGS

        $CC -c "src/parser.c" -o parser.o $FLAGS

        $CXX -shared -o $NAME.so *.o

        runHook postBuild