Fix and Re-Enable Python Testing on macos

[bashbaug]

To unblock an upcoming release, PR https://github.com/KhronosGroup/OpenCL-SDK/pull/103 disabled CI tests for Python on macos, since this appears to be a CI configuration issue and the Python samples have not changed. This issue is to track fixing the CI config for macos and re-enabling the Python testing.

For reference, the failure was:

-----------------------------------------------------------------------
RUNNING python/demo-array.py
-----------------------------------------------------------------------
ld: dynamic main executables must link with libSystem.dylib for architecture x86_64
error: linker command failed with exit code 1 (use -v to see invocation)
Final linking of kernel sum failed.
/Users/runner/work/_temp/2d4b9408-adac-48f3-b16a-fba1fc6c1105.sh: line 3:  7457 Abort trap: 6           python $i