Guard _Py_FFI_SUPPORT_C_COMPLEX for complex check in ctypes

# Bug report

### Bug description:

RHEL8 ships a libffi 3.1 which does not support complex types. _Py_FFI_SUPPORT_C_COMPLEX is not checked.

https://buildbot.python.org/#/builders/164/builds/2127

### CPython versions tested on:

CPython main branch

### Operating systems tested on:

_No response_


### Linked PRs
* gh-148969