fix bash to not build webapp when it is already built (#12834)

.circleci/config.yml

@@ -25,7 +25,9 @@ jobs:
           git checkout $CIRCLE_BRANCH || git checkout master
           export WEBAPP_GIT_COMMIT=$(git rev-parse HEAD)
           echo "$WEBAPP_GIT_COMMIT"
-          curl -f -o ./dist.tar.gz https://releases.mattermost.com/mattermost-webapp/commit/${WEBAPP_GIT_COMMIT}/mattermost-webapp.tar.gz && mkdir ./dist && tar -xvf ./dist.tar.gz -C ./dist --strip-components=1 || echo "curl failed" && export CURL_FAILED=1
+          export CURL_FAILED=0
+          curl -f -o ./dist.tar.gz https://releases.mattermost.com/mattermost-webapp/commit/${WEBAPP_GIT_COMMIT}/mattermost-webapp.tar.gz && mkdir ./dist && tar -xvf ./dist.tar.gz -C ./dist --strip-components=1 || export CURL_FAILED=1
+
           if [ $CURL_FAILED -eq 1 ]
           then
             npm ci && cd node_modules/mattermost-redux && npm install && npm run build && cd ../.. && make build