Apple Silicon Support

[nebhale]

Description

Now that Apple Silicon Macs are in the wild, darwin-aarch64 binaries should be created along with the darwin-arm64 binaries that are already created. The Homebrew formula should be updated to vend the proper binary as well.

Proposed solution

Using go1.16beta1 darwin/arm64 pack seems to build fine so I don't think there will be any technical issues.

➜ ~/d/s/b/pack main make
mkdir out/tests
> Building...
go build -ldflags "-s -w -X 'github.com/buildpacks/pack.Version=0.0.0+git-6033196' -extldflags " -trimpath -o ./out/pack -a ./cmd/pack
go: downloading github.com/pkg/errors v0.9.1
go: downloading github.com/spf13/cobra v1.1.1
go: downloading github.com/apex/log v1.9.0
go: downloading gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
go: downloading github.com/mattn/go-colorable v0.1.8
go: downloading github.com/buildpacks/lifecycle v0.10.1
go: downloading github.com/google/go-containerregistry v0.3.0
go: downloading github.com/Masterminds/semver v1.5.0
go: downloading github.com/buildpacks/imgutil v0.0.0-20201211223552-8581300fe2b2
go: downloading github.com/docker/docker v20.10.0-beta1.0.20201110211921-af34b94a78a1+incompatible
go: downloading github.com/opencontainers/image-spec v1.0.1
go: downloading github.com/sabhiram/go-gitignore v0.0.0-20201211074657-223ce5d391b0
go: downloading github.com/mattn/go-isatty v0.0.12
go: downloading github.com/mitchellh/ioprogress v0.0.0-20180201004757-6a23b12fa88e
go: downloading golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
go: downloading golang.org/x/mod v0.4.0
go: downloading gopkg.in/src-d/go-git.v4 v4.13.1
go: downloading golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
go: downloading github.com/containerd/stargz-snapshotter/estargz v0.0.0-20201217071531-2b97b583765b
go: downloading github.com/docker/cli v0.0.0-20200312141509-ef2f64abbd37
go: downloading golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f
go: downloading github.com/docker/distribution v2.7.1+incompatible
go: downloading github.com/opencontainers/go-digest v1.0.0
go: downloading github.com/sergi/go-diff v1.1.0
go: downloading gopkg.in/src-d/go-billy.v4 v4.3.2
go: downloading github.com/emirpasic/gods v1.12.0
go: downloading github.com/docker/go-units v0.4.0
go: downloading github.com/moby/term v0.0.0-20201110203204-bea5bbe245bf
go: downloading github.com/morikuni/aec v1.0.0
go: downloading github.com/opencontainers/selinux v1.6.0
go: downloading github.com/docker/go-connections v0.4.0
go: downloading github.com/containerd/containerd v1.4.1
go: downloading github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99
go: downloading github.com/opencontainers/runc v0.1.1
go: downloading github.com/sirupsen/logrus v1.7.0
go: downloading google.golang.org/grpc v1.33.1
go: downloading golang.org/x/net v0.0.0-20201202161906-c7110b5ffcbb
go: downloading github.com/src-d/gcfg v1.4.0
go: downloading github.com/kevinburke/ssh_config v0.0.0-20190725054713-01f96b0aa0cd
go: downloading github.com/mitchellh/go-homedir v1.1.0
go: downloading github.com/xanzy/ssh-agent v0.3.0
go: downloading gopkg.in/warnings.v0 v0.1.2
go: downloading google.golang.org/genproto v0.0.0-20201022181438-0ff5f38871d5
go: downloading github.com/golang/protobuf v1.4.3
go: downloading google.golang.org/protobuf v1.25.0
Time: 0h:00m:28s                                                                                                                                                 
➜ ~/d/s/b/pack main out/pack version                                     
0.0.0+git-6033196

It'll be fine to wait for a non-beta version of Go before releasing.

Describe alternatives you've considered

N/A

Additional context

N/A