build: update arm minimum supported platform

[gibfahn]

This is already true in practice.

Fixes: nodejs/build#1164

cc/ @nodejs/build @rvagg @gdams

@rvagg I'm not sure if this applies to arm (not arm64) as well.

[rvagg]

Correct for ARM64, not so much for other ARM. We test (and build) on Wheezy for ARMv6 and ARMv7, so that gives us glibc >= 2.13 for both of those. When you include kernel version things get even more complicated because the lowest we're running for ARMv7 is 3.2.34 but on ARMv6 we get 4.1.19 because we're using a Jessie boot setup to get the best out of our Pi's. I really don't know that we want to be that specific here.

I've argued against including kernel versions in here previously since it rarely matters when you account for libc and just makes things messy and complicated. I'm willing to bet that exactly zero people have found the kernel version we list helpful in any practical way.

[BridgeAR]

I guess this list is actually difficult to properly maintain. Is there any way we could automate something that produces a list of supported systems and their minimum build versions?

[rvagg]

@BridgeAR I guess an Ansible script or two to run across all our release- machines would get a pretty good picture? While we're at it the same thing could be run across all of test- to get a snapshot of what's actually in use.

[gibfahn]

I guess an Ansible script or two to run across all our release- machines would get a pretty good picture? While we're at it the same thing could be run across all of test- to get a snapshot of what's actually in use.

I think test- is probably more valuable than release- right? We don't actually check that node runs on the machines we build it on.

I guess in some cases we might have "experimental" or Tier 2 platforms that we build for but don't run CI on?

[gibfahn]

@rvagg I'm not sure if this applies to arm (not arm64) as well.

Correct for ARM64, not so much for other ARM.

Yeah, I figured that.

My vote would be for switching to a set of "these are the platforms we build and test on", but it seems wrong to leave the arm reference wrong. So how about I leave ARM as it was, and just change ARM64?

[rvagg]

yeah, put a lid back on that can of worms

[gibfahn]

CI: https://ci.nodejs.org/job/node-test-commit-light/387/

[mhdawson]

LGTM

[gibfahn]

CI: https://ci.nodejs.org/job/node-test-commit-lite/389/

[jasnell]

should this be backported to 8.x? If so, a separate backport PR is needed.