coreutils: Adjust coreutils dependency in each app to be selective

coreutils: Adjust coreutils dependency in each app to be selective

Adjust the dependency to the virtual coreutils main package in
each app to be selective. Otherwise you need to first select the
main coreutils before the actuall apps can be selected. That has
prevented other applications from depending on just one individual
coreutils app, as they have needed to depend also on the empty main
coreutils package.

Reference to discussion in:
https://github.com/openwrt/luci/issues/7605

Signed-off-by: Hannu Nyman <[email protected]>