My Junk PDB files aren't deleting

I somehow missed the part where Casey makes the junk pdb files delete automatically. Mine keep piling up and I have to delete them manually. Can somebody point me to the part of the stream where that happens? Thanks!
Day 22. From minute 11 to minute 17, Casey explains the setup that creates the pdbs with different filenames. Some seconds later, he explains that Visual Studio keeps the pdbs locked and that the build.bat can only get rid of them after Visual Studio is closed.
Thanks!