crossbuild attempts to compile unsupported openbsd-armv5

[stuartnelson3]

Crossbuild for master in alertmanager is failing on openbsd-armv5:

# openbsd-armv5

>> building binaries

 >   alertmanager

 >   amtool

# github.com/prometheus/alertmanager/vendor/golang.org/x/sys/unix

/go/src/github.com/prometheus/alertmanager/vendor/golang.org/x/sys/unix/flock.go:18: undefined: Flock_t

/go/src/github.com/prometheus/alertmanager/vendor/golang.org/x/sys/unix/sockcmsg_unix.go:36: undefined: Cmsghdr

/go/src/github.com/prometheus/alertmanager/vendor/golang.org/x/sys/unix/sockcmsg_unix.go:42: undefined: Cmsghdr

https://circleci.com/gh/prometheus/alertmanager/619

Looking at package x/sys/unix, the files the expected file for these definitions x/sys/unix/ztypes_openbsd_arm.go does not exist.

Checking against the site for supported platforms, they only have armv7:
https://www.openbsd.org/plat.html

Seems like this should be removed from the crossbuild?

[stuartnelson3]

cf. prometheus/alertmanager#723

[grobie]

Sounds good to me. I actually don't understand how we translate arm to arm5/arm6/arm7.

[sdurrheimer]

@grobie Nothing special, a hard-coded in the golang-builder / arm image.

[grobie]

@sdurrheimer So that means we can't easily just disable openbsd support vor ARMv5, but leave Linux support for ARMv5, right? Any suggestion how to handle this?

[sdurrheimer]

Need to rethink a little bit the system. I wasn't aware of such incompatibilities. I didn't play much with ARM.

[grobie]

Alternatively, maybe we can just disable all ARMv5 builds. @discordianfish Do you know whether ARMv5 is still widely in use?

[discordianfish]

It is, at least RPI 1+2 are armv5

[sdurrheimer]

Looking at this page
we should only support:

• linux: v5, v6, v7
• freebsd: v6, v7
• openbsd: v7
• netbsd: v6, v7

Am I right ?

[stuartnelson3]

That seems correct. As things change we can always update support, too.

[grobie]

Cool, so we can just replicate that matrix in the golang builder and fix this here?

[sdurrheimer]

I'm working on it, need to update both promu and golang-builder.