Update dist-(arm|armv7|armhf)-linux to Ubuntu 20.04

[nikic]

I believe this should be safe, as actual artifacts will be produced by a cross toolchain. The build ran through cleanly locally.

This came up in #93577, where the host GCC ICEd during the LLD build. (Though I wonder why we build LLD for the host at all...)

r? @Mark-Simulacrum

[Mark-Simulacrum]

We currently document ARMv6 Linux (kernel 3.2, glibc 2.17) as the support for arm-unknown-linux-gnueabi, which this builder produces.

I suspect that glibc 2.17 is older than even Ubuntu 18.04, but we probably should at least bump those docs alongside this PR. Since this target doesn't have a current maintainer, there's probably no one in particular to ping, though we could reach out to the Arm folks I suppose.

[nikic]

@Mark-Simulacrum Isn't the used kernel and glibc version controlled by the crosstool-ng config, rather than the host operating system? I thought the host OS is only relevant for cases where we don't use a cross toolchain (like the primary x86 dist builders).

[Mark-Simulacrum]

Ah, right. Yeah, that makes sense I think.

@bors r+ rollup

[bors]

📌 Commit e644fb5 has been approved by Mark-Simulacrum

[Mark-Simulacrum]

@bors rollup=iffy -- will need a docker cache re-population

[nikic]

In the interest of more efficient docker cache repopulation I've updated dist-armv7-linux as well. Based on a local run, that one works fine with ubuntu 20.04 as well.

[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit 6d2aa18 has been approved by Mark-Simulacrum

[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit 2c8c4f1 has been approved by Mark-Simulacrum

[bors]

⌛ Testing commit 2c8c4f1 with merge 1a8fa2a...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 1a8fa2a to master...

[rust-timer]

Finished benchmarking commit (1a8fa2a): comparison url.

Summary: This benchmark run did not return any relevant results.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression