Weird issues with Bash binary

[hwittenborn]

For some reason if my AppImage's entrypoint is a script with a #! bin/bash shebang, I get some weird behavior with the builtin Bash:

• Setting LD_LIBRARY_PATH doesn't seem to be respected by subprocess my entrypoint calls.
• The APPDIR variable can't be exported to subprocess without resorting to hacky workarounds.

Both of these cases are shown at https://github.com/hwittenborn/celeste/tree/main/appimage. I'm kind of clueless on how this is happening, part of me assumed there's some patching going on in the used Bash version or something, but I honestly haven't figured out anything besides a hacky workaround to alleviate the issues.