Fix install paths for cuquantum in CI and docs

[mlxd]

Before submitting

Please complete the following checklist when submitting a PR:

• All new features must include a unit test.
  If you've fixed a bug or added code that should be tested, add a test to the
  tests directory!

• All new functions and code must be clearly commented and documented.
  If you do make documentation changes, make sure that the docs build and
  render correctly by running make docs.

• Ensure that the test suite passes, by running make test.

• Add a new entry to the .github/CHANGELOG.md file, summarizing the
  change, and including a link back to the PR.

• Ensure that code is properly formatted by running make format.

When all the above are checked, delete everything above the dashed
line and fill in the pull request template.

---

Context: Current install directions for cuquantum allow use of the RPATH to the expected directory with Python, but requires explicit targets when using a C++ build. The docs and paths searched for cuquantum right now often have the lib dir implicit in the path, which causes an incorrect path to be found by CMake, as it is a child class of the root. This PR fixes those such paths, allowing the C++ builds to find the correct custatevec libraries, ensuring a successful cmake configuration step.

Description of the Change: As above.

Benefits:

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[mlxd]

Fixes current MPI-build block in #823

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.12%. Comparing base (186a1b1) to head (e5994a9).

Additional details and impacted files

@@                 Coverage Diff                  @@
##           fix_lgpu_aarch64     #831      +/-   ##
====================================================
+ Coverage             98.52%   99.12%   +0.60%     
====================================================
  Files                   114       99      -15     
  Lines                 18147    13243    -4904     
====================================================
- Hits                  17879    13127    -4752     
+ Misses                  268      116     -152     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[multiphaseCFD]

Thanks @mlxd ! Looks good to me! Does it mean that there will be a scenario that custatevec.so located in /lib64/ dir?

[mlxd]

Thanks @mlxd ! Looks good to me! Does it mean that there will be a scenario that custatevec.so located in /lib64/ dir?

No guarantee, but hard to know based on previous lib dirs I've seen in the wild.

[maliasadi]

I've never run into this issue before. nice catch! 🏉

[vincentmr]

LGTM, feel free to merge when the CI is green. Cheers and thanks @mlxd !

[maliasadi]

🏉

[multiphaseCFD]

Looks good to me! Thanks @mlxd !

[mlxd]

FYI, as this flows into #823 I'm ignoring formatting checks until post-merge