Set cmake PATH on macos to address libzstd flakiness (#91142)
This is to address the recent flakiness issue on MacOS ARM64 https://hud.pytorch.org/failure/Library%20not%20loaded%3A%20%40rpath%2Flibzstd.1.dylib.
From what I see, the immediate cause is that `cmake` exec under `/Users/ec2-user/runner/_work/_temp/miniconda/pkgs/cmake-3.22.1-hae769c0_0/bin/` is used instead of the expected one under the temp CONDA_ENV, i.e. `/Users/ec2-user/runner/_work/_temp/conda_environment_3736476178/bin`. I'm not quite sure what is the reason behind this flaky behavior, so I want to try a catch-all fix by setting the cmake PATH correctly
This PR also prints some debugging information w.r.t cmake PATH, and cleans up some legacy code in `macos-test.sh` script.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91142
Approved by: https://github.com/ZainRizvi
