x/sys: TestFstatat failures on dragonfly-amd64

[bcmills]

TestFstatat appears to be flaky on the Dragonfly BSD builder:

--- FAIL: TestFstatat (0.00s)
    syscall_unix_test.go:674: Fstatat: returned stat does not match Stat
FAIL
FAIL	golang.org/x/sys/unix	1.885s

Since the test output is not particularly useful, it's not clear to me whether this is a bug in x/sys, in the test itself, or in the Dragonfly kernel.

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CC @tklauser @tuxillo

[bcmills]

See previously #29401, #29447.

[tklauser]

Thanks for the report, I guess this is due to some Stat_t fields changing between the unix.Stat and unix.Fstatat, e.g. Stat_t.Atim. I think we should compare only certain fields, like we do in the same test for the unix.Lstat result already. Will send a CL.

[gopherbot]

Change https://golang.org/cl/265018 mentions this issue: unix: compare Stat_t members when checking Stat vs. Fstatat in TestFstatat