Shell variables in standalone app of bash script

I have a bash script that mounts a fuse filesystem created with the backup tool borg. Mounting the filesystem requires a passphrase. The mount command of borg allows to read the passphrase from an export in my shell script. So the first two lines of my script are something like

#!/bin/bash
export BORG_PASSPHRASE='mypassphrase'

Then I mount the filesystem with the mount command

borg mount user@server:/mntpoint::backup_repository /localmntpoint

The script runs perfectly fine. However, I would like to create a standalone app which runs this script. So I called the script Borg and created a directory Borg.app which contains Contents and MacOS as subdirectories and in MacOS I put the Borg shell script. This appears to be the usual way of turning a shell script into a clickable application. I am aware that one can click the shell script itself and a terminal will fire up and execute the script. I prefer the other option.

Unfortunately nothing happens upon clicking my Borg.app. I suspect the issue is the export command at the beginning which is somehow missed by the mount command in this setup.

Any help in resolving this is greatly appreciated.