cmake minimal version and CMP0148 warnings

[jkroonza]

whilst https://github.com/rpm-software-management/createrepo_c/commit/89fa02828cdaf1c710c38bde5fcbcf59538a9cce.patch pushes the minimum version to 3.7, newer cmake (4.1.2 in this case) reports:

CMake Deprecation Warning at CMakeLists.txt:1 (CMAKE_MINIMUM_REQUIRED):
  Compatibility with CMake < 3.10 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

And also this:

CMake Warning (dev) at src/python/CMakeLists.txt:13 (FIND_PACKAGE):
  Policy CMP0148 is not set: The FindPythonInterp and FindPythonLibs modules
  are removed.  Run "cmake --help-policy CMP0148" for policy details.  Use
  the cmake_policy command to set the policy and suppress this warning.

This warning is for project developers.  Use -Wno-dev to suppress it.

With the specific policy given as:

CMP0148
-------

.. versionadded:: 3.27

The ``FindPythonInterp`` and ``FindPythonLibs`` modules are removed.

These modules have been deprecated since CMake 3.12.
CMake 3.27 and above prefer to not provide the modules.
This policy provides compatibility for projects that have not been
ported away from them.

Projects using the ``FindPythonInterp`` and/or ``FindPythonLibs``
modules should be updated to use one of their replacements:

* ``FindPython3``
* ``FindPython2``
* ``FindPython``

The ``OLD`` behavior of this policy is for ``find_package(PythonInterp)``
and ``find_package(PythonLibs)`` to load the deprecated modules.  The ``NEW``
behavior is for uses of the modules to fail as if they do not exist.

This policy was introduced in CMake version 3.27.
It may be set by ``cmake_policy()`` or ``cmake_minimum_required()``.
If it is not set, CMake warns, and uses ``OLD`` behavior.

.. note::
  The ``OLD`` behavior of a policy is
  ``deprecated by definition``
  and may be removed in a future version of CMake.

[ppisar]

We know about the warnings. Question is whether we can or should raise the minimal version now. It could hinder people using systems with old cmake or python.

[jkroonza]

That remains your call whether or not to merge here, we need this to maintain compatibility on systems with newer cmake.