netty: Rebuild in IntelliJ takes a lot of time - NioEventLoop and ThreadDeathWatcher

For a big Gosu project, we are doing the performance analysis. There are about 100k Gosu files and other resources. On running the full rebuild, it takes about an hour. Disabling the anti-virus helped bringing this time to 30 minutes. 
On profiling this 30 min build, we see that most of the time is spent at io.netty.channel.nio.NioEventLoop.select() and io.netty.util.ThreadWatcher$Watcher.run() 
(Please see the screenshot)

Do you guys have any recommendation on how to fix / where to look for to improve the performance here?