cmd/go: test failure due to unexpected telemetry files left behind in temporary directory

[gopherbot]

#!watchflakes
default <- pkg == "cmd/go" && test == "" && `unexpected files left in tmpdir` && `telemetry[/\\]local`

Issue created automatically to collect these failures.

Example (log):

PASS
2026/03/27 02:36:28 unexpected files left in tmpdir: ["tmpdir342967640/mod_download1461785983/telemetry/local/go.test@devel-devel-linux-ppc64le-2026-03-27.v1.count" "tmpdir342967640/mod_download1461785983/telemetry/local/weekends"]
FAIL	cmd/go	102.179s

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "cmd/go" && test == ""

2026-03-27 02:11 gotip-linux-ppc64le_power8 go@91d1a883 cmd/go (log)

PASS
2026/03/27 02:36:28 unexpected files left in tmpdir: ["tmpdir342967640/mod_download1461785983/telemetry/local/go.test@devel-devel-linux-ppc64le-2026-03-27.v1.count" "tmpdir342967640/mod_download1461785983/telemetry/local/weekends"]
FAIL	cmd/go	102.179s

— watchflakes

[dmitshur]

This looks similar to #55260, but in this case it is some telemetry files being left behind. So far only happened once on a linux-ppc64le builder.

CC @golang/command-line.