Add a flag that saves the coverage output dir

This commit adds a pytest command line option `--no-cleanup` for
the coverage test. Running the coverage test with this option will
let users save the `kcov_output` directory so that it is easier to
inspect the coverage report.

Signed-off-by: Henry Wang <henry.wang@arm.com>

integration_tests/conftest.py

@@ -17,6 +17,13 @@ def pytest_addoption(parser):
             PROFILE_DEVEL
         )
     )
+    parser.addoption(
+        "--no-cleanup",
+        action="store_true",
+        default=False,
+        help="Keep the coverage report in `kcov_output` directory. If this flag is not provided, "
+             "both coverage related directories are removed."
+    )
 
 
 @pytest.fixture
@@ -24,6 +31,11 @@ def profile(request):
     return request.config.getoption("--profile")
 
 
+@pytest.fixture
+def no_cleanup(request):
+    return request.config.getoption("--no-cleanup")
+
+
 # This is used for defining global variables in pytest.
 def pytest_configure():
     pytest.profile_ci = PROFILE_CI