Change the test to compare lowercase font filenames and actually
check, if the original font is installed. Additionally drop currently
unused and already commented font mappings.

This also drops the single other tr and awk users to use $AWK instead.

Change-Id: I1886eeb9578386e3d8bdda6f011fcc9bc59eaa36
Reviewed-on: https://gerrit.libreoffice.org/7619Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>