Run the FreeBSD tests on GitHub Actions instead of Cirrus

[neilpang]

Closes #1640

Cirrus CI shut down on 2026-06-01, which removed the FreeBSD coverage. This
runs the same commands in a FreeBSD VM booted under QEMU/KVM on a regular
ubuntu-latest runner.

Both workarounds the Cirrus task carried are kept verbatim:

• LD_STATIC_TLS_EXTRA=4096 for Dependency of rustc_fluent_macros getting compiled with -Ztls-model=initial-exec rust#134863
• --skip-test test.rust-random/rand for rust-random/rand#1355

Verification

https://github.com/neilpang/rustc_codegen_cranelift/actions/runs/30730256715

22815 tests passed across 43 test binaries, 0 failed
job time 15m32s

cache-after-prepare skips the rustup install on subsequent runs.

[bjorn3]

Can you please remove the old cirrus ci config too. And please amend the commit message to remove the issue links.

View changes since this review

[clubby789]

Raised a fix to hopefully avoid needing the TLS workaround. rust-lang/rust#160522. Though I do want to note in my local VM testing I didn't encounter this error in FreeBSD 15, while I did in 13 and 14.

[neilpang]

All three done.

• .cirrus.yml removed.
• The push filter is gone, and timeout-minutes is 60.
• The commit message no longer carries the issue references; they are in
  the PR description instead.

On the timeout: this run took 15m25s, and the two before it 13m32s and
15m32s, so 60 leaves about four times the observed duration.

https://github.com/rust-lang/rustc_codegen_cranelift/actions/runs/30968473458/job/92187475340

@clubby789 I left LD_STATIC_TLS_EXTRA alone since the Readme documents it
as a FreeBSD requirement, but this job runs the 15.1 image, so if it would
help to know whether the workaround is still needed there I can drop it
and post the result.

[neilpang]

Removed. rustc.yml and cranelift-release-branch.yml do not set it either,
so this matches half the repo already.

[bjorn3]

Thanks!