Golang x/build: test failures are hard to discover

There has been a recent regression in the builder UI. Take this flake for example: if you click through to the log, there is no useful information besides FAIL: TestFoo; the stderr output has been removed. If you then click through (and crucially, know to do this) to the test JSON output, you find the name of the failing test, buried among thousands of lines of working-as-intended JSON framing information.

The primary stderr log should continue to show all of stderr.

Comment From: gabyhelp

Related Issues

• x/build/cmd/coordinator: failures are sometimes missing error output #39349 (closed)

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