Race between webhook and artifact contents

[niloc132]

Downloading the contents from the latest build after the webhook is sent means we sometimes get stale content.

The init script uses

gwtproject.org/www/init_content.sh

Lines 19 to 20 in a027510

	curl -L -o "$WORK_DIR/gwt-site.zip" https://nightly.link/gwtproject/gwt-site/workflows/build/main/gwt-site.zip
	curl -L -o "$WORK_DIR/gwt-site-webapp.zip" https://nightly.link/gwtproject/gwt-site-webapp/workflows/build/main/gwt-site-webapp.zip

to fetch the content, and sometimes this is still old after the webhook is sent indicating "the build is complete and artifact is ready". Either we need a more reliable event/link, or a small delay before fetching content.