Document phonopy cmake error troubleshooting

[ElliottKasoar]

When installing, I (and others) have encountered errors along the lines of:

CMake Error at /tmp/pip-build-env-j2jx9pp5/overlay/lib/python3.11/site-packages/nanobind/cmake/nanobind-config.cmake:243 (target_compile_features):
    target_compile_features The compiler feature "cxx_std_17" is not known to
    CXX compiler

    "GNU"

    version 4.8.5.
  Call Stack (most recent call first):
    /tmp/pip-build-env-j2jx9pp5/overlay/lib/python3.11/site-packages/nanobind/cmake/nanobind-config.cmake:358 (nanobind_build_library)
    CMakeLists.txt:108 (nanobind_add_module)


  -- Configuring incomplete, errors occurred!

  *** CMake configuration failed
  [end of output]

note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed building wheel for phonopy
Building wheel for python-hostlist (setup.py) ... done
Created wheel for python-hostlist: filename=python_hostlist-2.2.1-py3-none-any.whl size=39604 sha256=44f9f27a42895e61a521cf9129a6a3ad03e633b201390da5ef76d5f59db3b94f
Stored in directory: ...
Successfully built janus-core python-hostlist
Failed to build phonopy
ERROR: ERROR: Failed to build installable wheels for some pyproject.toml based projects (phonopy)

This isn't an issue with janus as such, but since users may be less familiar with cmake/compilers, a small troubleshooting section, e.g. suggesting ensuring compilers are identifiable and updated, may be useful.