The temporary directory may contain a dash, and the test shouldn't
fail because of that.
Fixesgolang/go#31164
Change-Id: I3c0d636771e13fec345e46394fb548e3c4ea4478
Reviewed-on: https://go-review.googlesource.com/c/tools/+/170177
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>