Rather than timing out dashing, run it in background (#62251)

https://github.com/flutter/flutter/issues/60646

dev/bots/docs.sh

@@ -54,13 +54,17 @@ function create_docset() {
   echo "$(date): Building Flutter docset."
   rm -rf flutter.docset
   # If dashing gets stuck, Cirrus will time out the build after an hour, and we
-  # never get to see the logs. Thus, we time it out after 30 minutes to see the
-  # logs.
-  (timeout '30m' dashing build --source ./doc --config ./dashing.json > /tmp/dashing.log 2>&1 || \
-  (echo 'Dashing failed! Tailing last 200 lines of log...'; tail -200 /tmp/dashing.log; exit 1)) && \
+  # never get to see the logs. Thus, we run it in the background and tail the logs
+  # while we wait for it to complete.
+  dashing build --source ./doc --config ./dashing.json > /tmp/dashing.log 2>&1 &
+  dashing_pid=$!
+  tail -f /tmp/dashing.log &
+  tail_pid=$!
+  wait $dashing_pid && \
   cp ./doc/flutter/static-assets/favicon.png ./flutter.docset/icon.png && \
   "$DART" --disable-dart-dev ./dashing_postprocess.dart && \
-  tar cf flutter.docset.tar.gz --use-compress-program="gzip --best" flutter.docset
+  tar cf flutter.docset.tar.gz --use-compress-program="gzip --best" flutter.docset && \
+  kill $tail_pid &> /dev/null
 }
 
 # Move the offline archives into place, after all the processing of the doc