Cyclic dependency prevents installation of python39 (also python3)

[Ronan Le Gallic]

Greetings to the Cygwin Team,

Description

  *
The setup.ini file introduces a circular dependency between python39, python39-pip, and python39-setuptools.
  *
This cycle blocks the installation of python39 and any packages that depend on it.

Configuration Snippet (from setup.ini)
```INI
@ python39
depends2: ..., python39-pip, python39-setuptools, ...

@ python39-pip
depends2: ..., python39, ...

@ python39-setuptools
depends2: ..., python39, ...
```

Consequences

  *
Prevents installation of python39, and so python3
  *
Also blocks installation of packages that depend on python39, such as:
     *
clang
     *
gdb

---
Best regards,
Ronan