Simplifies cross platform installation setup.py

[ooctipus]

Description

This PR

1. makes sure(skip if already satisfy, else install) the right torch is installed before and after pip installing isaaclab packages as sometime(rare case) due to flaky setup.py and unknown library dependencies changes pytorch version gets overriden.

2. only install pink and retargeters in linux x86 or amd64 machines

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[Mayankm96]

Looks good overall.

Mostly wondering why are we enforcing torch via the install script and not the pyproject.toml file. I think back then the motivation was to force install a specific torch version (different from one shipped with IsaacSim). But is this still needed?

[kellyguo11]

Looks good overall.

Mostly wondering why are we enforcing torch via the install script and not the pyproject.toml file. I think back then the motivation was to force install a specific torch version (different from one shipped with IsaacSim). But is this still needed?

I think it'd still be needed if we want to continue support for 4.5. We might also need to do something like this eventually when Isaac Sim removes the pytorch dependency to avoid issues on windows.