Add upstream patch to allow building on aarch64-apple-darwin

[shepmaster]

Closes #72

[shepmaster]

With this branch, I was able to cross-compile Cargo:

diff --git a/Cargo.toml b/Cargo.toml
index aa6be2f3d..fb8986e0c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -119,3 +119,6 @@ doc = false
 deny-warnings = []
 vendored-openssl = ["openssl/vendored"]
 pretty-env-logger = ["pretty_env_logger"]
+
+[patch.crates-io]
+openssl-src = { git = "https://github.com/shepmaster/openssl-src-rs",  branch = "aarch64-apple-darwin" }

% SDKROOT=$(xcrun -sdk macosx11.0 --show-sdk-path) MACOSX_DEPLOYMENT_TARGET=$(xcrun -sdk macosx11.0 --show-sdk-platform-version) cargo +462ec6baef52edea591eab1a070ed4e18b80d094 build --target=aarch64-apple-darwin --features vendored-openssl

    Finished dev [unoptimized + debuginfo] target(s) in 1m 34s

[alexcrichton]

Is it possible to test this on CI? Or do the macs on github actions not have the sdk installed?

[shepmaster]

Is it possible to test this on CI

It’s kind of a catch 22 situation. This change is needed to be able to build Cargo for aarch64 in Rust CI.

Right now, the only artifact you could use would be a random try build. With that, and some environment variables, you could cross compile to aarch64 on GitHub Actions or Azure Pipelines (haven’t looked at other CI providers).

None of the CI providers have aarch64 Darwin hardware, so you can’t actually run any tests.

[shepmaster]

Once rust-lang/rust#75991 is merged, then presumably those artifacts would be available to rustup in nightly, making it one step easier.

[alexcrichton]

Ah right sorry forgot that we needed a Rust target. In that case this looks good to me, thanks again @shepmaster!

[shepmaster]

I’ll try to submit a CI PR once the target lands in nightly. I assume that testing via cross compiling and with nightly should be ok?

[shepmaster]

Thanks!

[alexcrichton]

Yeah that'd be great! And yeah I don't expect to run tests, but it would be good to exercise the patching and building logic if we can.