runtime/cgo: build failing with `error: unknown warning group '-Watomic-alignment'` on `ios-arm64-corellium`

[bcmills]

Go version

24070cf

Output of go env in your module/workspace:

N/A

What did you do?

https://build.golang.org/log/85f674e744e8c08473b66ecef4d68f044f187e50

What did you see happen?

Building Go cmd/dist using /var/root/go-ios-arm64-bootstrap. (go1.20.6 ios/arm64)
Building Go toolchain1 using /var/root/go-ios-arm64-bootstrap.
Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1.
warning: unable to find runtime/cgo.a
Building Go toolchain2 using go_bootstrap and Go toolchain1.
# runtime/cgo
gcc_libinit.c:11:32: error: unknown warning group '-Watomic-alignment', ignored [-Werror,-Wunknown-warning-option]
go tool dist: FAILED: /tmp/workdir-host-ios-arm64-corellium-ios/go/pkg/tool/ios_arm64/go_bootstrap install -pgo=off cmd/asm cmd/cgo cmd/compile cmd/link: exit status 1

What did you expect to see?

All build steps succeeded and tests passing.

It appears that this flag was added in https://go.dev/cl/562348, for #65290 (attn @mauri870 @ianlancetaylor).

(attn @golang/ios)

[bcmills]

It isn't clear to me whether this problem is actually specific to ios, or more generally applicable but depending on a specific range of C compiler versions.

[gopherbot]

Change https://go.dev/cl/567556 mentions this issue: runtime/cgo: ignore unknown warning options

[mauri870]

I wonder if this is related to the clang that comes with xcode.

Maybe this approach works:

#if !defined(__has_warning) || __has_warning("-Watomic-alignment")
#pragma GCC diagnostic ignored "-Watomic-alignment"
#endif