Improve run.sh to handle empty labels and log to stdout (#237)

1. Print logs on standard output
2. Don't add labels if GITEA_RUNNER_LABELS not set

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/237
Reviewed-by: Jason Song <i@wolfogre.com>
Co-authored-by: Tomasz Duda <tomaszduda23@gmail.com>
Co-committed-by: Tomasz Duda <tomaszduda23@gmail.com>

scripts/run.sh

@@ -10,6 +10,10 @@ CONFIG_ARG=""
 if [[ ! -z "${CONFIG_FILE}" ]]; then
   CONFIG_ARG="--config ${CONFIG_FILE}"
 fi
+EXTRA_ARGS=""
+if [[ ! -z "${GITEA_RUNNER_LABELS}" ]]; then
+  EXTRA_ARGS="${EXTRA_ARGS} --labels ${GITEA_RUNNER_LABELS}"
+fi
 
 # Use the same ENV variable names as https://github.com/vegardit/docker-gitea-act-runner
 
@@ -26,10 +30,7 @@ if [[ ! -s .runner ]]; then
       --instance "${GITEA_INSTANCE_URL}" \
       --token    "${GITEA_RUNNER_REGISTRATION_TOKEN}" \
       --name     "${GITEA_RUNNER_NAME:-`hostname`}" \
-      --labels   "${GITEA_RUNNER_LABELS}" \
-      ${CONFIG_ARG} --no-interactive > /tmp/reg.log 2>&1
-
-    cat /tmp/reg.log
+      ${CONFIG_ARG} ${EXTRA_ARGS} --no-interactive 2>&1 | tee /tmp/reg.log
 
     cat /tmp/reg.log | grep 'Runner registered successfully' > /dev/null
     if [[ $? -eq 0 ]]; then