fix(tests): clear test artifacts dir before test runs

Before each test run, we copy artifacts from the build/artifacts/ path
to /srv/test_artifacts. This directory was not cleared up though, which
led to issues with artifact A/B testing, where A's artifacts persisted
and were selected by pytest over B's artifacts.

To prevent this, clear the test artifacts dir at the beginning of each
run.

Signed-off-by: James Curtis <jxcurtis@amazon.co.uk>

Author: JamesC1305

tools/test.sh

@@ -36,7 +36,8 @@ if [ "${FC_TEST_SKIP_ARTIFACT_COPY:-}" = "1" ]; then
   say "Skipping artifact copy (FC_TEST_SKIP_ARTIFACT_COPY=1)"
 elif [ -f build/current_artifacts ]; then
   say "Copy artifacts to /srv/test_artifacts, so hardlinks work"
-  cp -ruvfL $(cat build/current_artifacts) /srv/test_artifacts
+  rm -rf /srv/test_artifacts/*
+  cp -rvfL $(cat build/current_artifacts)/. /srv/test_artifacts/
 else
   # The directory must exist for pytest to function
   mkdir -p /srv/test_artifacts