cmd/go: TestScript/build_runtime_gcflags failing on longtest builder

[ALTree]

The TestScript harness is currently broken, causing a failure in the cmd/go test suite on the longtest builder. A log:

https://build.golang.org/log/13f2837122b3a012cc7d46fe08e0214ca5ee61fb

The failures started at 0005515 (cmd/go: fix -n output in runtime/internal/atomic).

cc @jayconrod

[mvdan]

That's when the test script was added. Weirdly enough, the test script passes on my machine.

Also, I think the comment on the test script is wrong. It says "See golang.org/issue/26092.", but that issue seems completely unrelated to the build flags bug.

[gopherbot]

Change https://golang.org/cl/156237 mentions this issue: cmd/go: fix failure in TestScript/build_runtime_gcflags

[jayconrod]

This was a misconception on my part. I assumed the tests were using separate caches. This issue could be reproduced by running go build -gcflags=all=-l std before running the test.

The test will now creates its own cache directory.

(Also, fixed the issue URL. Thanks for pointing that out.)