test: run-test.sh now works inside a container

The `run-test.sh` helper is meant to execute the tests as if it
was CI but using a container. If it is detected that we are
already running inside a container assume it is prepare so that
we can exectue the tests directly and do so.

run-tests.sh

@@ -4,12 +4,21 @@ set -euo pipefail
 SHELLCHECK_SEVERITY=${SHELLCHECK_SEVERITY:-warning}
 
 run_test() {
+  if [ -f /.dockerenv ]; then
+    eval "$1"
+    return
+  fi
+
   podman run --rm -it -v "$(pwd)":/github/workspace:z --env "GITHUB_WORKSPACE=/github/workspace" koji.test "$1"
 }
 
-pushd test
-podman build -t koji.test -f Dockerfile .
-popd
+if [ ! -f /.dockerenv ]; then
+  pushd test
+  podman build -t koji.test -f Dockerfile .
+  popd
+else
+  echo "Container detected, direct mode."
+fi
 
 SCRIPTS="$(git ls-files --exclude='*.sh' --ignored | xargs echo)"