Every now and again I run into a problem where cleaning my Android build folder just doesn't work. You can use File Explorer, gradle, even WSL with a `sudo rm -rf app/build`, yet I am still unable to delete it. It's usually a single file that gets stuck. A reboot will certainly fix it, but there is a much simpler way!

Press Win+R and type resmon then click OK
Click the CPU tab and open Associated Handles
Type the stuck file's name into the search box
Look for adb.exe, java.exe, or some other Android related process
Right-click and select End Process

Now try deleting doing whatever Windows refused to do before. Coming from macOS and Linux I find this pretty silly. If you operate with admin privileges you should be able to completely own the file system, for better or worse. In this case, you are probably just trying to do your job and some tool got stuck.