Really appreciate the response, @Retired_mod.  So using your advice, I tried commenting out various parts of the script, but kept getting an error of the type: "Init script failure:
Cluster scoped init script /Users/XYZ/gdal_install.sh failed: Script exit status is non-zero"

The only thing that worked was:

apt-get update

I'm trying to install gdal on a Databricks Runtime Version 13.2 ML.  Thanks, Sean