Oh. my god. That was it. At least a great portion of it. Build time went down to 3,2 seconds average from 6.2. That’s almost a 100% performance increase.
THANK YOU!!! I’ve been wondering about this for about half a year, and switched to Ubuntu for that period of time for this reason alone. Not that I hate Ubuntu, but there are a bunch of other quirks with Ubunu which still make me want to develop in Windows. I might go back now 
That said, there’s still a bit to go to Ubunut’s 2.5 second average…Might be just the NTFS file system that is slower - now at least it is the same build speed for the project when mounted on Ubuntu NTFS, and Windows.
edit 4.2 was javac build. Gradle was even better - 3.2s! Guess because of parallelization?
Table updated, with data on Windows without antivirus:
