mips64 build fix

[lucasbergman]

Just a quick drive-by fix for the linux/mips64 builds so I can export metrics from my EdgeRouter 😄

[SuperQ]

Hell yes to getting node_exporter for EdgeRouters,
but I think we need to do some more work to get the promu stuff fixed so we don't break other platforms.

[lucasbergman]

@SuperQ Thanks! I ran [blah blah GOPATH] promu crossbuild -p linux/mips64; promu tarballs and got a working output. I thought that was enough to re-enable the relevant archs in .promu.yml, but I admit I don't understand the environment here very well.

Shall I make this pull request include just the build tag fix 4f479e5 and sort out the promu business separately? Is there some other validation I can/should run?

[SuperQ]

@sdurrheimer Any comment here?

[SuperQ]

Yes, I think splitting out the uname syscall change into a separate PR would be good. I think the cgo issue is going to be solved on the promu side.

[sdurrheimer]

We can't disable cgo like that because this will break other platforms.

node_exporter is quite complicated by the fact that it use a lot of "direct systems features", some platforms can be build without cgo and works perfectly fine, others need to be built with cgo like darwin for example.

I'm currently not so sure this is a promu problem, but we might have to improve promu to handle more successfully edge cases like in the node_exporter.

[lucasbergman]

@SuperQ Done, this PR contains only 4f479e5 now. The Circle failure looks spurious. Is that broken at master?

@sdurrheimer 😊 Oops, I see there are a ton more cgo dependencies left for BSD and Solaris, sorry; I misunderstood the commit message for 2ee8470. Now that I'm nerd sniped by this, I'll play around to see if I can get linux/mips working with promu and cgo; it looks like the builder image has something bogus going on with its installed system headers for MIPS cross builds.

[SuperQ]

Sorry for the delay in getting this reviewed. Let us know if you make progress on getting the cross builds working better. It'd be nice to be enable as many platforms as we can for node_exporter.

[lucasbergman]

Thanks for the merge, folks. I'll be in touch. 😄