os: TestChtimes failure on OSX with Go 1.10: AccessTime didn't go backwards

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.10 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOBIN=""
GOCACHE="/Users/me/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/me/go"
GORACE=""
GOROOT="/Users/me/opt/go"
GOTMPDIR=""
GOTOOLDIR="/Users/me/opt/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/cf/y_tt0zms6nx39x08k23y5zsr0000gn/T/go-build648291915=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

$ GOROOT_BOOTSTRAP=~/opt/go-bootstrap ./all.bash

What did you expect to see?

(tests pass)

What did you see instead?

--- FAIL: TestChtimes (0.00s)
        os_test.go:1200: AccessTime didn't go backwards; was=2018-02-20 14:13:29.321904999 +0200 EET, after=2018-02-20 14:13:29.322166175 +0200 EET
FAIL
FAIL    os      0.759s