smb: split module into two targets of which one is a static lib
Summary:
this allows us to use the intermediate static target for unit testing
(which we'll want for smburl at the very least).
the effective output remains unchanged, we simply have a fake library
now before we turn it into a proper plugin .so.
kdemain as a result was moved to its own file and only gets built into the
final plugin but not the static library as it'd not have any use there
anyway
Test Plan: builds and works still
Reviewers: ngraham, apol
Reviewed By: apol
Subscribers: apol, kde-frameworks-devel, kfm-devel
Tags: Dolphin, Frameworks
Differential Revision: https://phabricator.kde.org/D27800