Use the qualified dart command path.

Author: isoos

setup.sh

@@ -110,5 +110,5 @@ if [[ "${ACTIONS_ID_TOKEN_REQUEST_URL}" != "" && "${ACTIONS_ID_TOKEN_REQUEST_TOK
 then
   PUB_TOKEN=$(curl --retry 5 --retry-connrefused -sLS "${ACTIONS_ID_TOKEN_REQUEST_URL}&audience=https://pub.dev" -H "User-Agent: actions/oidc-client" -H "Authorization: Bearer $ACTIONS_ID_TOKEN_REQUEST_TOKEN" | jq -r '.value')
   echo "PUB_TOKEN=${PUB_TOKEN}" >> $GITHUB_ENV
-  dart pub token add https://pub.dev --env-var PUB_TOKEN
+  ${RUNNER_TOOL_CACHE}/dart-sdk/bin/dart pub token add https://pub.dev --env-var PUB_TOKEN
 fi