make aarch64-unknown-linux-gnu a default instead of i686-unknown-linux-gnu

[programmerjake]

basically no one uses i686-unknown-linux-gnu except for legacy comparability, imo aarch64-unknown-linux-gnu would be a better default. i686 still gets tested by default in i686-pc-windows-msvc which afaik is much more widely used still.

inspired by: rust-lang/blog.rust-lang.org#1720

[syphar]

can you provide some sources / input about the old targets usage and the better default?

For the mac targets I had the promote/demote RFCs, is there something I can check for your proposal?

[programmerjake]

Debian and Fedora are two Linux distros that are widely used as a base for other Linux distros:
https://www.debian.org/releases/trixie/release-notes/issues.en.html#reduced-support-for-i386
https://fedoraproject.org/wiki/Changes/Drop_i686_support

why aarch64: it's tier 1, also https://github.blog/changelog/2024-09-03-github-actions-arm64-linux-and-windows-runners-are-now-generally-available/

[syphar]

looking at the [tier 1 target list], and the default targets today on docs.rs we build for:

• aarch64-apple-darwin
• i686-pc-windows-msvc
• i686-unknown-linux-gnu (**should be remove?)
• x86_64-pc-windows-msvc
• x86_64-unknown-linux-gnu

we currently intentionally don't build all tier 1 targets.
These are missing in our list

• aarch64-pc-windows-msvc (added 2025/08/22)
• aarch64-unknown-linux-gnu
• x86_64-pc-windows-gnu

So, I definitely see that we could add aarch64-unknown-linux-gnu, because it's tier 1, and people use it.
We'll have to watch build durations to see if the imact is too high. Currently we only have limited build-server capacity.

About removing i686-unknown-linux-gnu from the list: your comment and the linked pages make sense to me. I wonder if we can have that decision confirmend by others? (@GuillaumeGomez might have an opinion?). Or who else could confirm this?

[GuillaumeGomez]

I'd remove it as well. If it's less used, there isn't really a point keeping it. Do you want me to send the PR for removing it?

[syphar]

#2943