fix: run KISS modem unit tests in CI via native_kiss_modem env

The new test_kiss_modem suite needs KissModem headers and sources that
only native_kiss_modem provides. Scope native to test_utils and run both
envs in the unit test workflow.

.github/workflows/run-unit-tests.yml

@@ -20,7 +20,7 @@ jobs:
         uses: ./.github/actions/setup-build-environment
 
       - name: Run Unit Tests
-        run: pio test -e native -vv
+        run: pio test -e native -e native_kiss_modem -vv
 
       - name: Upload Test Results
         # Upload test results even if the test step failed.

platformio.ini

@@ -163,6 +163,7 @@ build_flags = -std=c++17
   -I src
   -I test/mocks
 test_build_src = yes
+test_filter = test_utils
 build_src_filter =
   -<*>
   +<../src/Utils.cpp>