cmd/go: cache log grows unbounded and go clean -cache ignores it

[4a6f656c]

On a go builder with limited disk, I have a ~/.cache/go-build/log file that is more than 0.5GB in size - it would appear that this log grows unbounded, which seems like a bad thing. Furthermore, go clean -cache cleans out the cache but leaves the log file around (I have a cronjob that runs go clean -cache daily since the cache also grows unbounded and fills the disk otherwise - see #29561).

[bradfitz]

What version of Go?

I thought this was already fixed. Or we at least already had a bug open for it.

[4a6f656c]

It's a builder, so it should be whatever it is currently building (although I guess it could also be originating from the go-bootstrap in use).

[4a6f656c]

FWIW the go-bootstrap version is go version devel +99e4ddd053 Tue Dec 18 00:13:58 2018 +0000 openbsd/arm.

[bradfitz]

Did you mean log.txt or actually log?

#25323 & https://go-review.googlesource.com/c/go/+/167741/

[4a6f656c]

Sorry, log.txt - ah, excellent - I'll update the go-bootstrap and you can mark this as a duplicate.