Support arm64

[runesoerensen]

This PR adds the linux/arm64 target in buildpack.toml.

For testing the buildpack, an arm64 compatible builder can be created locally (using the newly released heroku-24 base images (tested on an m1 Mac with Docker's containerd feature enabled), and a basic builder configuration file) - e.g. something like this:

builder-24/builder.toml:

description = "Heroku-24 (Ubuntu 24.04) builder sans buildpacks"

[stack]
id = "heroku-24"
build-image = "heroku/heroku:24-build.nightly"
run-image = "heroku/heroku:24.nightly"

[lifecycle]
version = "0.19.0"

Create the builder:

pack builder create heroku/builder:24 --config ./builder-24/builder.toml

Compile and package the CNBs:

cargo libcnb package

cargo libcnb package --target aarch64-unknown-linux-musl

To test that the x86_64 version still work as intended, we need to use the old builder (asheroku/builder:24 won't work for multi-arch locally):

pack build go-amd64-app \
--buildpack packaged/x86_64-unknown-linux-musl/debug/heroku_go \
--path buildpacks/go/tests/fixtures/basic_http_122 --builder heroku/builder:22

To test aarch64:

pack build go-arm64-app \
--buildpack packaged/aarch64-unknown-linux-musl/debug/heroku_go \
--path buildpacks/go/tests/fixtures/basic_http_122 --builder heroku/builder:24

Running the commands twice should reuse cached layers as usual. Another app can be used to verify cache invalidation, e.g.:

pack build go-arm64-app \
--buildpack packaged/aarch64-unknown-linux-musl/debug/heroku_go \
--path buildpacks/go/tests/fixtures/basic_http_119 --builder heroku/builder:24

This can also be tested with an integration test in buildpacks/go/tests/integration_tests.rs (and a similar test should be added when heroku/builder:24 is available in the registry):

#[test]
#[ignore = "integration test"]
fn test_go_arm64() {
    TestRunner::default().build(
        BuildConfig::new("heroku/builder:24", "tests/fixtures/basic_http_116")
            .target_triple("aarch64-unknown-linux-musl"),
        |ctx| {
            assert_contains!(
                ctx.pack_stdout,
                "Installing go1.16.15 (linux-aarch64) from https://go.dev/dl/go1.16.15.linux-arm64.tar.gz",
            );
        },
    );
}

See comment below for creating an arm64 builder on an amd64 host.

[joshwlewis]

To test this, I had to modify your example steps. Since I'm on an Intel-based Mac, my builder.toml looked like this:

description = "Heroku-24 (Ubuntu 24.04) builder sans buildpacks"

[stack]
id = "heroku-24"
# Direct reference to heroku/heroku:24 arm64 variant image by sha
build-image = "heroku/heroku@sha256:860714147f7deb5540aada42db1028d88204bf1ba0ded8209663c5d4d55d423d"
# Direct reference to heroku/heroku:24-build arm64 variant image by sha
run-image = "heroku/heroku@sha256:ef63d62be65d145f7db1f11257691b294b5dcc302ffe14a33185884780572e1c"

[lifecycle]
version = "0.19.0"

But it worked, and that's awesome!

[joshwlewis]

and a similar test should be added when heroku/builder:24 is available in the registry

Yes, definitely. Is this tracked somewhere so we don't forget?

[runesoerensen]

and a similar test should be added when heroku/builder:24 is available in the registry

Yes, definitely. Is this tracked somewhere so we don't forget?

Yep, I just created an issue for it #239 :)