x/build/cmd/watchflakes: fails to attribute `*** Test killed with quit:` failures to the running test

[bcmills]

In #57995 (comment), I see a test failure ending in:

*** Test killed with quit: ran too long (4m0s).
FAIL	bytes	240.041s

but watchflakes matched that to the explicit condition test == "" .

This pattern should be fairly easy to match, so watchflakes should attribute these failures to the correct package's tests.

(attn @cherrymui)

[bcmills]

Hrm, and then when I excluded Test killed with quit from #57995, watchflakes filed #61071 with the correct package path.

So maybe the bug here is that test == "" incorrectly matches failures that have a non-empty test?

[cagedmantis]

/cc @golang/release for visibility