feat(riscv64): add RISC-V build support to devcontainers and CI

[gounthar]

Description

Add RISC-V (rv64gc) build support to the Ocre Runtime devcontainers and Zephyr CI pipeline.

WASI-SDK only ships pre-built host binaries for x86_64 and arm64. On other architectures (notably riscv64), the current mkdir && curl | tar unconditionally fails. This PR makes the WASI-SDK install conditional in both Dockerfiles and adds the riscv64 Zephyr toolchain + QEMU board to CI.

This builds on PR #188 (merged), which added the OCRE_BUILD_DEMO_CONTAINERS cmake option to skip demo container cross-compilation when WASI-SDK is absent.

• Related to issue fix: make demo container building optional via cmake option #188

Type of change

• New feature (non-breaking change which adds functionality)
• CI system update

How Has This Been Tested?

Three full native builds on a Banana Pi F3 board, building all three sample apps (mini, demo, supervisor) with the Linux variant. The cmake fix from #188 combined with the conditional WASI-SDK install in this PR allows a clean end-to-end build.

Blog post with full build logs and verification: https://bruno.verachten.fr/2026/02/24/WebAssembly-on-RISC-V-Banana-Pi-F3/

Test Configuration (required):

• Host OS type, version, and arch: Debian Trixie (riscv64)
• Developer Board make & model: Banana Pi F3 (SpacemiT K1, rv64gc, 16 GB RAM)
• Board Tools Installed: cmake, gcc, make, git

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[kr-t]

Hi @gounthar , thanks for the PR!

It seems we have permission issues for pushing packages from forks during the PR check. We will think of the current design and how to fix these restrictions.

[casaroli]

Hello, thank you for you contribution.

We have plans to increase build platform support by using the ubuntu provided clang + wasi-sysroot + runtime lib. I hope this will be implemented soon, so we won't need the "binary" wasi-sdk installed.

I would prefer to do use it instead, because it will make the containers consistent across multiple platforms.

For this reason, I suggest we keep this PR as draft for now, and we rework/merge parts of it when RISCV64 support is "officially" added.

Please bear with me 😅

[gounthar]

@casaroli Thanks for the context; that makes total sense. Using Ubuntu's clang + wasi-sysroot will be much cleaner across platforms.

I'll convert this to draft. Happy to help test or rework when you're ready to add riscv64 officially. In the meantime, the fork at https://github.com/gounthar/ocre-runtime works for anyone who needs it now.

[casaroli]

Please see this PR: #193
and the related PR in ocre-sdk: project-ocre/ocre-sdk#15

[casaroli]

this was cherry-picked into #196