fix connectivity unit test for --enable-mergedlibs

it's a workaround, but given the conflicting requirements of
MSVC not liking duplicate symbols, but the unit test needing to
link the objects directly to access internal symbols, there is
not much else we can do.

Change-Id: I9bdcc5f2b6ab0712cc3317033c4fbae4791cbb6b
Reviewed-on: https://gerrit.libreoffice.org/12387
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>