Add android build support

[malbarbo]

This add android build support, including openssl.

[rust-highfive]

r? @alexcrichton

(rust_highfive has picked a reviewer for you, use r? to override)

[malbarbo]

There is some interest on using rust on android (termux/termux-packages#261). rustup already has android build support.

Even if cargo is being build with rust, I think it is good to have a docker image to build cargo.

What about the travis android build? Should I remove it?

[bors]

☔ The latest upstream changes (presumably #3878) made this pull request unmergeable. Please resolve the merge conflicts.

[alexcrichton]

Thanks for the PR!

Note though that the builds in this repository are going to be retired very soon. We're not actually making releases based on these builds any more right now, so these artifacts will just get gc'd at some point.

It looks like no code changes happened here though? In that case I'd be ok to add a builder to verify that we can keep compiling for android, but otherwise maybe we should hold off until a PR can be made to rust-lang/rust?

[malbarbo]

There is no code change.

In that case I'd be ok to add a builder to verify that we can keep compiling for android

Verify that cargo can be compiled for android (before rust-lang/rust/ is updated) is a good thing.

I made a PR to add android host builders: rust-lang/rust#41149.

[alexcrichton]

Ok, perhaps we can pare this down to just one Android target? I suspect we won't need to test all android targets in full before changes reach rust-lang/rust

[malbarbo]

Ok, perhaps we can pare this down to just one Android target?

That's makes sense. I update the PR.

[alexcrichton]

@bors: r+

Thanks!

[bors]

📌 Commit f723268 has been approved by alexcrichton

[bors]

⌛ Testing commit f723268 with merge a319155...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: alexcrichton
Pushing a319155 to master...