[CMAKE] Fix OSX native build

Summary:
Cross building for OSX is working, but native cmake build on OSX is
missing some -framework directives to link bitcoin-qt because there
is no QT .prl files to get the dependencies from.
Note that this is the same behavior that autotools build.

Test Plan:
On OSX:

mkdir buildcmake && cd buildcmake
cmake -GNinja ..
ninja

Check the build is successful. Run the generated bitcoin-qt as a
sanity check.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D3791