Add Rust activation for linux-riscv64

[lijkang]

Summary

• add linux-riscv64 activation variants for stable Rust and rust_dev
• use the riscv64gc-unknown-linux-gnu target and the RISC-V GCC linker
• use the Linux RISC-V glibc 2.39 baseline
• verify that the test executable is a RISC-V ELF binary

Context

This provides the rust_linux-riscv64 activation package used by {{ compiler("rust") }} for Linux RISC-V builds.

This depends on conda-forge/rust-feedstock#297 providing the corresponding Rust compiler and rust-std-riscv64gc-unknown-linux-gnu package. The newer riscv64a23 target is not selected here because #297 currently builds the riscv64gc host target.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe/meta.yaml) and found it was in an excellent condition.

I do have some suggestions for making it better though...

For recipe/meta.yaml:

• ℹ️ The recipe is not parsable by parser conda-souschef (grayskull). This parser is not currently used by conda-forge, but may be in the future. We are collecting information to see which recipes are compatible with grayskull.
• ℹ️ The recipe is not parsable by parser conda-recipe-manager. The recipe can only be automatically migrated to the new v1 format if it is parseable by conda-recipe-manager.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/31567365833. Examine the logs at this URL for more detail.}

[lijkang]

@conda-forge-admin, please rerender

[luhenry]

@lijkang conda-forge/rust-feedstock#297 was merged and rust-std-riscv64gc-unknown-linux-gnu is available

[luhenry]

@conda-forge-admin, please rerender

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-webservice.

I tried to rerender for you, but it looks like there was nothing to do.

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/31513458946. Examine the logs at this URL for more detail.}

[luhenry]

@conda-forge-admin, please restart ci

[luhenry]

Submitted the admin-request for adding rust_linux-riscv64 at conda-forge/admin-requests#2259

[dbast]

@conda-forge-admin, please restart ci

[dbast]

@conda-forge-admin please rerender