CMake: Fix linking of greentea, unity and utest

[LDong-Arm]

Requires: ARMmbed/mbed-os#14880

The test application uses the greentea client for synchronization with the host and unity for assertions, and unity in Mbed OS contains references to utest. We have recently split them from one mbed-greentea library into three, so the test application needs to link all of them.

Notes:

• The communication between device and host does not currently work, because currently the integration of greentea-client + Mbed OS has an I/O issue. Nonetheless, it does not affect this PR because the version of greentea-client is controlled by Mbed OS which we always use the latest version of.
• Once this gets in, we need to rebase the branch tfm_latest_integration_check to take advantage of the fix too.

[LDong-Arm]

From Travis:

9.98s$ pip install -r mbed-os/requirements.txt
0.35s$ python3 test_psa_target.py -t GNUARM -m ${TARGET_NAME} --cli=2 -b
[Test-Target] 10:10:54: "mbedgt" is not installed. Exiting...

But mbed-os/requirements.txt does contain mbed-greentea.

[Patater]

Travis is failing because mbed-os-tools use a newer prettytable with Python 3 than icetea supports. PR ARMmbed/mbed-os#14880 will fix.

[LDong-Arm]

Manually started a nightly run that points to this PR.

[Patater]

ARMmbed/mbed-os#14880 has been merged

[LDong-Arm]

Forced pushed to rerun Travis

[Patater]

Travis still appears to be caching Python dependencies.

Processing /home/travis/.cache/pip/wheels/46/60/6c/bb25d05df22906786206e901e9354bb3061061191116768bee/prettytable-0.7.2-py3-none-any.whl

[Patater]

I'll clear the cache on Travis

[Patater]

Cleared cache for this PR. Rerunning Travis...

[Patater]

Boo, still using cached old prettytable for some reason. I'll clear all cache.

[rwalton-arm]

Boo, still using cached old prettytable for some reason. I'll clear all cache.

Is caching pip installed dependencies a good idea? Dependencies (and transitive dependencies) change so frequently we'd always want to start from a clean environment, I'd assume.

[LDong-Arm]

Even though we removed icetea, requirements.txt still has an old prettytable listed (using == instead of >=): https://github.com/ARMmbed/mbed-os/blob/master/requirements.txt#L3 maybe this needs an update?

[Patater]

Even though we removed icetea, requirements.txt still has an old prettytable listed (using == instead of >=): https://github.com/ARMmbed/mbed-os/blob/master/requirements.txt#L3 maybe this needs an update?

Gah, that looks like the issue. Good spot.

[Patater]

Raised ARMmbed/mbed-os#14940

[Patater]

Merged that mbed-os PR, cleared Travis cache for this PR, and re-kicked it off

[LDong-Arm]

Thanks @Patater, it's finally resolved! 🎉