Disable shellcheck unused variables warnings in compile section
Disable shellcheck unused variables warnings in compile section

This duplicates the changes from the "cleaning" part of the lab that tell `shellcheck` to skip the warnings about a few "global" Bats variables being "unused". (They are used by the `bats-file` library, but `shellcheck` can't figure that out.)
UMM-CSci-Systems/Command-line-introduction