App Center allows you to use build scripts for some level of customization with builds.
If you clicked "Save & Build" after modifying scripts, and you see App Center running the Build Script step, for instance,
– without actually executing the contents inside, chances are, it's because of the line endings.
Please note that these Bash scripts are run on a Mac machine. So they are expected to have UNIX style line endings (LF).
If you're using Windows to edit/create these scripts, please ensure they're saved with the Unix (LF) format. I use Notepad ++ for this,
Ensure from the menu, Edit -> EOL Conversion -> Unix (LF) is selected.