The `group` expression ensures that the cancel-in-progress
behavior is to only cancel if a new commit is pushed to the PR for
which the job is running, not other PRs.

This is a fairly standard snippet, used also in CI jobs for NumPy
and other projects.

This is a follow-up to gh-4271. At the moment, when a contributor
pushes the latest `develop` to their own branch to bring their own
fork in sync with `main`, or if they push another branch, this triggers
30 CI jobs to run. Most will complete silently and only burn CPU
time unnecessarily. If there's a failure, this may result in unexpected
failure notifications. And the AWS Graviton3 run won't complete at all
and time out, since the Cirun hook will only work when triggered from
the main repo.

I noticed this because GitHub emailed me that it would disable the
nightly job because it hadn't changed for 3 months. It currently takes
30-50 minutes daily, and by default runs on all forks of the main
repository that have the relevant workflow yaml file. That serves little
purpose and wastes quite a bit of energy - so disable the runs outside
of the main repo.

This will not disable the runs on forks already made in the past that
contain this workflow file, but it does save 3 months worth of runs on
every new fork that is created.

[skip ci]

Set up arm64 graviton CI using cirun

LoongArch64 CI

CI (C910V): add test

Signed-off-by: Han Gao <gaohan@iscas.ac.cn>

add NO_INSTALL_FROM_API to re-enable --HEAD

Signed-off-by: Alex <aleksandrosansan@gmail.com>

Signed-off-by: Alex <aleksandrosansan@gmail.com>

Signed-off-by: Alex <aleksandrosansan@gmail.com>

CI (MSYS2): Configure with `-DCMAKE_BUILD_TYPE=Release`.

Add cross compile tests without running checks. Currently
only mips64el, riscv64, mipsel, alpha is wired up.
Just help us make sure those less popular CPUs are not
messed up by changes.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>

Re-organize build matrix for Ubuntu and MacOS runners.
Don't start runners that don't do anything.
Run tests.

...as homebrew has dropped at least gcc8 now

default 11.3.1 in the github image is causing brew to fail with "outdated xcode" message

Also, add comments to clarify what the test is testing