Move ARM Linux support to Tier 1

[mmatyas]

Currently the following ARM Linux targets are in Tier 2:

• arm-unknown-linux-gnueabi
• arm-unknown-linux-gnueabihf
• armv7-unknown-linux-gnueabihf
• aarch64-unknown-linux-gnu

However, all of them have official rustc, std and cargo builds, and they are available via rustup. According to the builders page, it seems some of them do have running automatic tests, eg. auto-linux-64-cross-armhf.

What I'd like to ask is, what's left to do to move these targets to Tier 1? Are there any problems, any blocker issues? Or some other reason?

[mmatyas]

Oh, I just noticed the tests are actually skipped...
Other than that, is there something else necessary?

[sanxiyn]

The blocking issue is running tests. QEMU was suggested to run tests, see #33114.

[alexcrichton]

Yeah the definition of Tier 1 is that we're running tests, which we currently aren't doing. We're also arguably lacking documentation for these platforms as they haven't seen as much usage as the x86/x86_64 platforms. In any case though this is largely covered by #33114, so I'm gonna close in favor of that, but thanks for the report!