Add redux build for when webapp needs to be built in server side (race condition). (#15380)

.circleci/config.yml

@@ -28,7 +28,7 @@ jobs:
           export WEBAPP_GIT_COMMIT=$(git rev-parse HEAD)
           echo "$WEBAPP_GIT_COMMIT"
 
-          trap 'npm ci && make build' ERR
+          trap 'npm ci && cd node_modules/mattermost-redux && npm i && npm run build && cd - && make build' ERR
           curl -f -o ./dist.tar.gz https://pr-builds.mattermost.com/mattermost-webapp/commit/${WEBAPP_GIT_COMMIT}/mattermost-webapp.tar.gz
           mkdir ./dist && tar -xvf ./dist.tar.gz -C ./dist --strip-components=1
           trap - ERR