For me, this happened because of an active debugging process. So, before cleaning or rebuilding, make sure to kill all active processes. To nail down the success, execute Invalidate Caches/Restart.
If you are testing with a local backend (java servlet on local google app engine) the running process blocks some files. So you are not able to live deploy. So in this case you can solve this by stopping the local backend before starting clean or build. You find the option under "Run -> Stop backend".
I have tried to remove all the Java services but still it is failing while executing the gradlew clean build command from IntelliJ terminal. I even verified the other applications I have opened somewhere the same path which I am trying the delete. But could not find any of such. So, finally restarted the IntelliJ IDE and able to proceed build smoothly. 2b1af7f3a8