Working directories are now set seperately from the commands so they
can later be swapped out when running linters over projects is
supported, and also better support filename mapping for running linters
on other machines in future.
As discussed in w0rp/ale#1051, there are cases where it would be useful
to be able to specify the dialect explicitly. This commit allows users
to do so using the ale_sh_shellcheck_dialect variable.
Fixes: w0rp/ale#1051
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>