community/fwupd: upgrade fails without bash

Hello,

When I upgraded my alpine linux from 3.15 to 3.15.1, I encountered an error with grub.

The file /etc/grub.d/35_fwupd contains the shebang #! /bin/bash which produces an error when APK calls grub-mkconfig and bash isn't installed. I had to install bash and then execute apk fix.

So it seems there is two solutions:

• Add bash as dependency for grub (not really satisfying IMHO)
• Rewrite this config part so it doesn't need bash (and possibly submit it upstream)