I just ran a full test pass (I am unusual because I do this during toolset updates) and it consumed about 200 gigs (newly expanded by ASAN configurations) and I ran out of space on my drive. I had long been aware that full test passes consumed a lot of space, but this was the first time it caused so much trouble.

There's no reason we need to keep emitted .obj and .exe files after a test has run. IIRC, the test harness creates fresh subdirectories for each configuration. Can we delete those subdirectories when we're done with them, so a full test pass won't permanently consume any space?