hdf5: add cxxstd variant

[balos1]

No description provided.

[hyoklee]

Hi, @balos1 ! Thank you for your contribution. Would you please fix Python code style and make CI pass?

[balos1]

@spackbot style

[balos1]

CC @white238

[balos1]

@spackbot fix style

[spackbot-app]

Let me see if I can fix that for you!

[spackbot-app]

I was able to run spack style --fix for you!

spack style --fix

repos/spack_repo/builtin/packages/acts_algebra_plugins/package.py
repos/spack_repo/builtin/packages/detray/package.py
repos/spack_repo/builtin/packages/duckdb/package.py
repos/spack_repo/builtin/packages/exiv2/package.py
repos/spack_repo/builtin/packages/gnupg/package.py
repos/spack_repo/builtin/packages/green_mbpt/package.py
repos/spack_repo/builtin/packages/hdf5/package.py
repos/spack_repo/builtin/packages/llvm/package.py
repos/spack_repo/builtin/packages/memcached/package.py
repos/spack_repo/builtin/packages/mfem/package.py
repos/spack_repo/builtin/packages/py_cython/package.py
repos/spack_repo/builtin/packages/py_scikit_build_core/package.py
repos/spack_repo/builtin/packages/py_slepc4py/package.py
repos/spack_repo/builtin/packages/slepc/package.py
�[1;34m==> �[0mrunning flake8
�[1;34m==> �[0mrunning isort
�[1;34m==> �[0mrunning black
�[1;34m==> �[0mstyle checks passed

Keep in mind that I cannot fix your flake8 or mypy errors, so if you have any you'll need to fix them and update the pull request. If I was able to push to your branch, if you make further changes you will need to pull from your updated branch before pushing again.

I've updated the branch with style fixes.

[hyoklee]

The default C++ standard is C++11.