empty column to display as '--' instead of modify the csv file, which I am parsing in some other scripts (and loading on Google spreadsheets), lets change them only when piping to `column` which has the bug https://man7.org/linux/man-pages/man1/column.1.html#BUGS Bug: 283139160 Test: `./incremental_build.sh -c "no change" -b soong prod -- nothing` Change-Id: I4c7a3c3670082e6cc11adf3d123c0ad824a4cb58