Pass BUILD_THREADS args to runner container

[idigs]

Enable passing the following variables to the runner container:

• BUILD_THREADS
• BUILD_THREADS_SYSTEM_TEST

For some reason I had a failing unit test on my ISIS runner, and it only passes if I restrict the number of unit tests running in parallel. It's a 64-core machine and it failed with 64 parallel and 60 parallel tests, but passes with 50 parallel tests. thomashampson/mantid_github_actions_test#3.

Now I'm at the point of those failing system tests so can investigate that.

It's this test here that fails:
https://github.com/mantidproject/mantid/blob/b4d934695ddf02bb8418e38392bb152c3def09d8/Framework/LiveData/test/MonitorLiveDataTest.h#L126

I have seen similar behavior before. With 64 core ornl builders, I set BUILD_THREADS=56 and BUILD_THREADS_SYSTEM_TESTS=12

this aligns exactly what we do with the ISIS 32 core ones, where we have BUILD_THREAD=28 and BUILD_THREADS_SYSTEM_TESTS=6

I guess we might want to be able to pass an argument to the github-runner docker container to specify this

[idigs]

Still seeing the same issue for ornl runners
https://github.com/idigs/mantid_github_actions_test/actions/runs/21071579883/job/60602379572?pr=5

[idigs]

One suggestion is to incorporate logic:

• the ratio of the BUILD_THREADS value is 7/8 of that numbers of cores on the host system
• the ratio of the BUILD_THREADS_SYSTEM_TESTS value is 3/16 of that numbers of cores on the host system

Modify build script here to set these values:

https://github.com/mantidproject/mantid/blob/3f9591dd19beec3a5f0672bcbc6c788473383b14/buildconfig/Jenkins/Conda/conda-buildscript#L45

if [[ -z "$BUILD_THREADS" ]]; then
    if [[ $OSTYPE == 'darwin'* ]]; then
        BUILD_THREADS="$(sysctl -n hw.logicalcpu)"
    else
        BUILD_THREADS="$(grep -c ^processor /proc/cpuinfo)" # Not physical but logical cores, includes hyper threaded.
    fi
fi

[idigs]

mantidproject/mantid@main...idigs:mantid_github_actions_test:idigs-patch-6

[idigs]

thomashampson/mantid_github_actions_test#3