ipython fails to install on Cygwin due to psutil not supporting Cygwin, despite documentation claiming ipython supports Cygwin

Pretty simple problem. I can provide whatever other information you may need on request.

The ipython documentation [claims that Cygwin is supported](https://ipython.readthedocs.io/en/stable/overview.html#portability-and-python-requirements).

I'm running Cygwin 3.6.9 on Windows 11 Professional with Python 3.12.12 and Pip 26.0.1. I'm installing it from within an active virtualenv created with `python -m venv`.

`pip install ipython`, which works on all other platforms, fails on Cygwin with the following error output:

```
$ pip install ipython
...
Collecting psutil>=7 (from ipython)
  Downloading psutil-7.2.2.tar.gz (493 kb)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error

  x Getting requirements to build wheel did not run successfully.
  | exit code: 1
  ╰—> [1 lines of output]
      platform cygwin is not supported
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed to build 'psutil' when getting requirements to build wheel
$
```

I was able to successfully get it to install without error using `pip install colorama decorator ipython-pygments-lexer jedi matplotlib-inline pexpect pygments stack_data traitlets` followed by `pip install --no-deps ipython`. It appears to work fine so far (I have not exercised all of the capabilities yet).

Note that, despite my having installed this in a virtualenv, I get the following startup warning from ipython:

```
$ ipython
/cygdrive/C/...../venv/lib/python3.12/site-packages/IPython/core/interactiveshell.py:986: UserWarning: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.
  warn(
Python 3.12.12 ...
...
In [1]:
...
```

The `ipython` command in use _is_ installed in the virtualenv, for sure:

```
$ which ipython
/cygdrive/C/...../venv/bin/ipython
```

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