Cortex R52 and Rust library support

[matthewjrichey]

In this pull request I have added:

• support for building Rust for Cortex-R52 cores using the armv8r-none-eabihf target
• support for building Rust libraries into C applications

[d3zd3z]

Sorry I haven't gotten around to reviewing this until now. Both of these seem quite reasonable, although I don't have a way to directly test. Is there a cortex-R target in Zephyr we can use to do a build test in CI?

[d3zd3z]

Don't worry about the Doc preview. I need to work with Zephyr ops to figure out how to get PRs from clones to have the credentials.

[matthewjrichey]

Thank you for reviewing.

There are Zephyr Cortex R targets, but I'm not sure about what CI resources are available to run Cortex R builds. Also I do not know much about how the Zephyr project automates its testing or what CI-related requirements they specify for public code submissions. I am sure this is documented somewhere, I'll need to look for it.

Generally, as far as you know, do all repos in the zephyrproject-rtos github organization (or, does zephyr-lang-rust in particular) follow the same guidelines with respect to CI requirements?

[nashif]

There are Zephyr Cortex R targets, but I'm not sure about what CI resources are available to run Cortex R builds.

*** Booting Zephyr OS build v4.1.0-rc2-9-g3e75ce132ddf ***
Hello World! qemu_cortex_r5/zynqmp_rpu

:)

[matthewjrichey]

Hi everyone. What can I do to build some more traction on this PR? Discussion so far has been about CI, are we stalled here? What exactly needs to be done on the CI front to move this forward?

Thanks!