Integrate embench-iot as benchmark suite

[yc199911]

embench-iot provides 19 benchmarks designed for embedded systems, offering more representative coverage than the existing dhrystone. This complements the current benchmark infrastructure and enables more thorough performance evaluation of rv32emu.

• Add embench-iot as a git submodule under tests/embench-iot
• Add rv32emu board support (boardsupport.c/h) in the fork
• Add wrapper Makefile to bridge rv32emu build system with scons
• Register embench-iot in TEST_SUITES in mk/artifact.mk
• Add scons to CI install dependencies
• Update CI to detect changes under tests/embench-iot

Note: This integration requires sysprog21 to create an official fork of embench-iot (similar to sysprog21/ansibench) and update the submodule URL accordingly before merging.

Close #28

---

Summary by cubic

Integrates embench-iot as a new benchmark suite for rv32emu, adding 19 embedded-focused tests to improve coverage beyond Dhrystone. Hooks it into the build, CI, and artifact pipeline for repeatable runs.

• New Features

  • Add embench-iot as a git submodule under tests/embench-iot.
  • Add rv32emu board support and a wrapper Makefile to build via scons.
  • Register the suite in TEST_SUITES in mk/artifact.mk.
  • CI: install scons and detect changes under tests/embench-iot.

• Migration

  • Create an official sysprog21/embench-iot fork and update the submodule URL before merging.

^{Written for commit 6f1ea41. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

---

Since this is your first cubic review, here's how it works:

• cubic automatically reviews your code and comments on bugs and improvements
• Teach cubic by replying to its comments. cubic learns from your replies and gets better over time
• Add one-off context when rerunning by tagging @cubic-dev-ai with guidance or docs links (including llms.txt)
• Ask questions if you need clarification on any suggestion

[jserv]

Note: This integration requires sysprog21 to create an official fork of embench-iot (similar to sysprog21/ansibench) and update the submodule URL accordingly before merging.

This approach should be avoided initially. The only valid reason to fork an existing benchmark suite is if it has not been maintained for some time. If you encounter build or runtime errors in embench-iot, please submit a pull request upstream first.

[yc199911]

Submitted two PRs to upstream embench-iot to avoid maintaining a separate fork:

1. fix(wikisort): replace custom bool typedef with stdbool.h
   fix(wikisort): replace custom bool typedef with stdbool.h embench/embench-iot#215
2. Add rv32emu board support
   Add rv32emu board support embench/embench-iot#216

While testing embench-iot with a GCC 15 toolchain (which defaults to C23),
I encountered a build failure in wikisort caused by typedef uint8_t bool —
since bool is now a language keyword in C23.
embench-iot#215 addresses
this by replacing the custom bool definitions with #include <stdbool.h>.

Once these are merged upstream, I will update this PR to point the
submodule directly at the upstream repo, removing the need for a fork.