Add arm64 build option

[duffn]

This adds an arm64 build option.

❯ node release/build.js --os darwin --arch arm64
Using user-specified OS darwin
Using user-specified arch arm64

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 Showing tool versions
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📜 node --version
v22.11.0
📜 go version
go version go1.23.4 darwin/arm64
📜 date +%s
export CGO_CFLAGS=-mmacosx-version-min=10.10
export CGO_LDFLAGS=-mmacosx-version-min=10.10
Compiling binary
export GOOS=darwin
export GOARCH=arm64
export CGO_ENABLED=1
📜 go build -ldflags "-X github.com/itchio/butler/buildinfo.Version=head -X github.com/itchio/butler/buildinfo.BuiltAt=1735830626
 -X github.com/itchio/butler/buildinfo.Commit= -w -s"
# github.com/itchio/sevenzip-go/sz
glue.c:119:29: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]

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 Packaging...
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📜 mv butler ./artifacts/darwin-arm64/butler
📜 file ./artifacts/darwin-arm64/butler
./artifacts/darwin-arm64/butler: Mach-O 64-bit executable arm64
📜 ./artifacts/darwin-arm64/butler -V
head, built on Jan  2 2025 @ 08:10:26
📜 ./artifacts/darwin-arm64/butler fetch-7z-libs
📜 go test -v ./butlerd/integrate --butlerPath='/Users/nicholasduffy/code/butler/artifacts/darwin-arm64/butler'
# github.com/itchio/sevenzip-go/sz

# .... tests here

ok      github.com/itchio/butler/butlerd/integrate      8.896s

Notes

• Of course, I can't test the itch.io executable signing, so commented that out in my testing.
• The build results in this:

❯ uname -a
Darwin me.local 23.6.0 Darwin Kernel Version 23.6.0: Fri Nov 15 15:13:15 PST 2024; root:xnu-10063.141.1.702.7~1/RELEASE_ARM64_T6000 arm64

❯ file ./artifacts/darwin-arm64/butler
./artifacts/darwin-arm64/butler: Mach-O 64-bit executable arm64

❯ ./artifacts/darwin-arm64/butler -V
head, built on Jan  2 2025 @ 08:13:58

Related issues

• This should resolve Recognize arm64 as a valid goarch itch#2928