KDb: Better support for ICU
Summary:
- KDb: ICU is required
- KDb: prepend craft's lib dir to LIB path so find_package(ICU) finds our files. Otherwise it is possible that find_package(ICU) finds some random private copies such as those coming with MSVS.
NOTE: maybe make this fix general purpose by always prepending 'lib' dir to LIB?
Test Plan: craft kdb
Reviewers: Craft, vonreth
Reviewed By: Craft, vonreth
Subscribers: vonreth, Craft
Differential Revision: https://phabricator.kde.org/D10760