x/sys/unix: OpenBSD: MAP_CONCEAL missing except on arm64

[awnumar]

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

$ go version
go version go1.12.9 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output

$ go env
xpslinux :: ~ » go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/awn/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/awn/src/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build069259099=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Received a report of a compile fail due to the MAP_CONCEAL flag being missing on OpenBSD.

What did you expect to see?

Expected to see it defined since it is supported on OpenBSD: https://man.openbsd.org/mmap.2#MAP_CONCEAL

What did you see instead?

A grep of the code-base shows that it is indeed defined, but only on ARM64: https://github.com/golang/sys/blob/2aa67d56cdd77167a5fb51358e8c3ce04bad68bb/unix/zerrors_openbsd_arm64.go#L927

[smasher164]

./mkall.sh probably needs to be re-run on OpenBSD >= 6.5
/cc @ianlancetaylor @bradfitz @tklauser

[gopherbot]

Change https://golang.org/cl/198157 mentions this issue: unix: update openbsd/{386,amd64.arm} MAP_* consts