Remove dedicated test target to CI pipeline

Target "test_ga" for dedicated test workflow is removed. Instead, check
if environment variable GITHUB_ACTIONS is set to detect which
environment is running the test.

GITHUB_ACTIONS is set to "true" automatically when running CI workflow
on github actions. It is documented in the link below.

Link: https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/store-information-in-variables#default-environment-variables
Change-Id: I9359514623d96dfa387524a67c9de34d94b87c5c

Author: SimonLiu423

Makefile

@@ -58,11 +58,11 @@ check: qtest
 
 test: qtest scripts/driver.py
 	$(Q)scripts/check-repo.sh
-	scripts/driver.py -c
-
-test_ga: qtest scripts/driver.py
-	$(Q)scripts/check-repo.sh
-	scripts/driver.py -c --group-output
+	$(Q)if [ -n "$$GITHUB_ACTIONS" ]; then \
+		scripts/driver.py -c --group-output; \
+	else \
+		scripts/driver.py -c; \
+	fi
 
 valgrind_existence:
 	@which valgrind 2>&1 > /dev/null || (echo "FATAL: valgrind not found"; exit 1)