When installing an extension, the CLI must to select the correct
binary to download for the machine (see the
[`installBin` function](78c1d00ecc/pkg/cmd/extension/manager.go (L240))).
By default, the CLI will download a binary matching the current
machine's architecture.
However, to provide better support for Macs running on Apple
Silicon, it will
[fall back](78c1d00ecc/pkg/cmd/extension/manager.go (L267-L274))
from `darwin-arm64` to `darwin-amd64` if
[Rosetta](https://support.apple.com/en-gb/102527) (Apple's
compatibility layer) is installed.
If Rosetta isn't installed, this fallback doesn't happen, which
can lead to surprising and confusing results when one Mac has
Rosetta and another doesn't, because the extension will install
on one machine but not another.
In the situation where a `darwin-arm64` binary isn't available
but the CLI can't fall back to `amd64` because Rosetta isn't
installed, this updates our error message to suggest installing
Rosetta.
Closes https://github.com/cli/cli/issues/9592.
a0a2567354