Fix build on FreeBSD by re-using Akonadi compile options

Akonadi may require exceptions; if so, these are in its interface target properties. Because kmail (and kmailpart) link privately to kmailprivate, which in turn links privately to Akonadi, but both kmail and kmailpart include Akonadi headers, we end up with a mismatch: Akonadi wants exceptions, but its consumers (kmail and kmailpart) don't know that.

Fix this by explicitly pulling in the relevant options.