libtorch: exclude from libomnibus to support multipy usage from pybind (#81672)
Summary: When libtorch is bundled into libomnibus all of the symbols are marked as unexported which causes issues when deploy/multipy tries to link in a subinterpreter at runtime. This excludes `libtorch` and `ATen-core` from libomnibus so the symbols remain exported and available.
Test Plan:
stacked diff
```
buck2 test @//mode/opt -c python.package_style=inplace //multipy/runtime:test_deploy_from_python
```
Differential Revision: D37946374
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81672
Approved by: https://github.com/PaliC
