For now, we mostly use "/bin/sh" for background tasks; but sometimes
we call it as "sh". The former does not work on android, but I'm not
yet sure how we should fix that.
Let's make things consistent first, so they are easier to change
(we might remove some background tasks, or reimplement them in fish
script).
In POSIX sh, ";" is not a valid statement, leading to errors when the
__fish_cached callback argument has a trailing newline (5c2073135e
(Fix syntax error in __fish_print_port_packages.fish, 2025-11-14)).
Use a newline instead of ";", to avoid this error.
While at it, replace rogue tab characters.
