CI: Test on Linux arm64 runners

[seisman]

xref:

• https://github.blog/changelog/2025-01-16-linux-arm64-hosted-runners-now-available-for-free-in-public-repositories-public-preview/
• https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories

[weiji14]

Test failures on some x2sys_cross tests appear to be the same as #3194, we had some logic to handle the shape mismatches using an if sys.platform == "darwin" check, e.g. here:

https://github.com/GenericMappingTools/pygmt/blob/8a09f75cae034ab0e01e1a29e46df65a116d9508/pygmt/tests/test_x2sys_cross.py#L273-277

Maybe we can use if platform.machine() == "arm64" to handle both Ubuntu and macOS arm64 variants, xref https://docs.python.org/3/library/platform.html#platform.machine?

[seisman]

Maybe we can use if platform.machine() == "arm64" to handle both Ubuntu and macOS arm64 variants, xref https://docs.python.org/3/library/platform.html#platform.machine?

platform.machine() returns arm64 on macOS ARM and aarch64 on Linux ARM. So, if platform.machine() in {"aarch64", "arm64"}: works, but there are still two failures related to contour.

[seisman]

Maybe we can use if platform.machine() == "arm64" to handle both Ubuntu and macOS arm64 variants, xref https://docs.python.org/3/library/platform.html#platform.machine?

platform.machine() returns arm64 on macOS ARM and aarch64 on Linux ARM. So, if platform.machine() in {"aarch64", "arm64"}: works, but there are still two failures related to contour.

I've marked the two 'contour' tests as xfail on Linux ARM and now all tests pass.