Support ARM builds for macOS

[chriskrycho]

At WWDC 2020, Apple announced upcoming Macs will ship with ARM processors. We'll want to add support for those as soon as makes good sense:

• when Rust itself supports the target architecture
• once someone has a dev kit we can use for testing (this may end up being me, since I have interest for side projects)

This is currently blocked:

• Rust support should come quickly, since Apple's ARM 64 targets are already in the general support matrix—but are currently Tier 2 targets per the Forge, and Rust will need to do some work to bump that up to a Tier 1 support category. (Presumably the existing aarch64-apple-ios is the same architecture, which could make an interesting situation name-wise. 😂)
• Getting a dev kit is a matter of applying for one and being approved. I'll investigate on that front since it's potentially of interest to me anyway.

[charlespierce]

Another blocker to be aware of: Currently there are no ARM builds of Node for MacOS. There are Linux ARM64 builds, which I believe Volta supports (though it needs to be manually compiled since we don't create pre-packaged binaries for it), but as of right now there aren't any pre-built Node binaries to download for darwin-arm64

[chriskrycho]

Indeed! I actually just mentioned as much in my application for a dev kit. 🤞

[jrock2004]

I just tried install Volta on linux and its not supported. So maybe it makes sense to get linux working first?

[chriskrycho]

@jrock2004 can you elaborate? We definitely have a bunch of users on Linux, so are you meaning Linux with ARM specifically?

[jrock2004]

@chriskrycho This is what I get

[chriskrycho]

Thanks for the report! Which OS and what architecture are you running?

[jrock2004]

Ubuntu server for raspberry pi 4 on ARM

[chriskrycho]

Thanks! That's helpful, and it is a great suggestion as a starting point here!

[charlespierce]

@jrock2004 That's true, as I noted above, we don't currently create pre-built binaries that work with our installer for Linux in ARM. I do believe that Volta itself supports that architecture, but it would require building from source, which may or may not be feasible for your use-case.

It unfortunately looks like GitHub actions doesn't currently support architectures other than x86_64, so that could be a blocker for both creating a Linux + ARM build and for this issue. My first test would be to try with cargo cross and see if we can make a cross-architecture build, but I don't know much about that.

[rwjblue]

Could we use Docker for ARM on Linux?

[charlespierce]

One other thing to consider, we should implement #34 as well as checking the architecture when trying to download Node, so we know if the version is available for the Mac + ARM combination.

[chriskrycho]

Note: the relevant architecture is now a Tier 2 supported target; I will see if I can give this a go on my DTK next week. (And hey, maybe not too long after than, on regular hardware!)

[jasonsilberman]

Just wanted to check in on this, how are things going?

[chriskrycho]

Haven't had a chance to poke at it yet, but my discussions with the Rust folks working on it indicated (a) it should be pretty straightforward to build, including automated builds once GitHub Actions supports it, and (b) the Rosetta version should work just fine in the meantime.

[charlespierce]

A couple of notes that we'll probably need to fix even once things compile:

• The installer showing an error for ARM architecture, if we detect MacOS + ARM we should treat that the same as x64 (at least until we support M1 natively, then we should handle it correctly)
• Once we have M1 support, we'll need to have a plan for Node versions: Newer versions will start to include native builds, but older versions we'll need to fall back to the x64 and rely on Rosetta. We should also include that in the documentation so users know that about older versions.

[charlespierce]

Done in the 1.0.1 release! Also added #919 to track supporting M1 native Node builds once they become available.