[CMAKE] Add resource file to bitcoin-qt

Summary:
The resource file is missing from bitcoin-qt in the windows build. Other
executables have the resource file set correctly.

Test Plan:

Cross build for Windows with CMake. Check the `bitcoin-qt.exe`

executable embeds its icon.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D4256