Added support for Clear Linux in install-required-packages.sh. (#8154)

* Disable shellcheck 2034 due to computed variable names.

This particular check throws a large number of false positives in this
file because it cannot see us using the mappings from packages to
per-distro package names since we're accessign them through computed
variable names.

* Add Clear Linux support to install-required-packages.sh

This adds preliminary support for Clear Linux to the
install-required-packages script, which allows users to use the regular
kickstart install script there.

As of right now, this has a significant limitation in that Clear Linux
does not provide a package for libJudy, meaning that users will not be
able to use the dbengine.