Latest Ubuntu GitHub runner causes OpenMP tests to fail in CI

[bryanpkc]

From the CI job (https://github.com/flang-compiler/classic-flang-llvm-project/actions/runs/7309478286/job/19992674439) for PR #170:

Failed Tests (2):
  libomp :: affinity/kmp-affinity.c
  libomp :: affinity/omp-places.c

Even though there have been recent changes to the CI workflows, this particular job as specified in .github/workflows/llvm-project-tests.yml has not been updated. Comparing the failing run with a previous passing run (https://github.com/flang-compiler/classic-flang-llvm-project/actions/runs/6562896746/job/17825903837), it can be seen that both are using the ubuntu-latest runner (Ubuntu 22.04.3), and running the same commands to build and test the compiler.

One noticeable difference between the two is that the passing run had only two threads available (llvm-lit reported -- Testing: 66155 tests, 2 workers --), while the failing run had four threads on two cores. I suspect that the enablement of SMT on the runner, or the configuration of the Linux kernel on the runner, had somehow caused these tests to fail.

I propose to exclude these tests from the CI workflows for this repository.