[CMAKE] Fix cmake check-functional dependencies

Summary: test_runner.py does not need bitcoin-test-util.py to run, but requires bitcoin-cli for some tests.

Test Plan:
Run:

cmake -DBUILD_BITCOIN_CLI=OFF -GNinja .. && ninja check-functional

It should return:
ninja: error: '../src/bitcoin-cli', needed by 'test/CMakeFiles/check-functional', missing and no known rule to make it

Should return no error (clear the cache first):

cmake -GNinja .. && ninja check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2498