Add Cmake flag to ensure we're propagating thread_count

[reazulhoque]

Thread count is not being propagated to Cmake. This fixes that.

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[magnatelee]

@reazulhoque please add the sign key to your GitHub account. the policy is that we don't accept PRs with unverified or unsigned commits.

[magnatelee]

also I don't recall we had any issue with the parallel build... can you describe what you're trying to fix with this PR?

[reazulhoque]

@magnatelee We are propagating to cmake what users have provided with -j flag to install.py.

Without this fix user provided option will not be respected by cmake.

[manopapad]

To be clear, install.py does pass -j directly to ninja/make, which is the last stage of the build, and covers all C++ compilation. We would have to pass this to cmake if we were using cmake --build rather than ninja/make directly. The problem is that compilation of the rust profiler expects to read -j from cmake.

[manopapad]

If you can, please also open a corresponding PR on https://github.com/nv-legate/legate.core.