fix bug when compile with native cuda arch

[USTCKAY]

Type

• Bug fix (non-breaking change which fixes an issue): Fixes #
• New feature (non-breaking change which adds functionality). Resolves #
• Breaking change (fix or feature that would cause existing functionality to not work as expected) Resolves #

Motivation and Context

Checklist:

• I have run python util/check_style.py --apply to apply Open3D code style
  to my code.
• This PR changes Open3D behavior or adds new functionality.
  • Both C++ (Doxygen) and Python (Sphinx / Google style) documentation is
    updated accordingly.
  • I have added or updated C++ and / or Python unit tests OR included test
    results (e.g. screenshots or numbers) here.
• I will follow up and update the code if CI fails.
• For fork PRs, I have selected Allow edits from maintainers.

Description

Fix Invalid architecture string bug when compile with native cuda arch by default, cmake error report is below:

[update-docs]

Thanks for submitting this pull request! The maintainers of this repository would appreciate if you could update the CHANGELOG.md based on your changes.

[USTCKAY]

@benjaminum @ssheorey Hi, could you please help to take a review?

[ssheorey]

Hi @USTCKAY can you confirm that the changes work for you? i.e. cmake configures correctly with this change? Also what version of cmake are you using?

[USTCKAY]

Hi @USTCKAY can you confirm that the changes work for you? i.e. cmake configures correctly with this change? Also what version of cmake are you using?

Yeah，cmake could complete and build could succeed after applying this change. My cmake version is 3.30.5, and I compiled Open3D in docker with image pytorch/pytorch:2.5.1-cuda12.1-cudnn9-devel.