Only suppress Python warnings on new enough CMake (#139)

* Older CMake doesn't have the policy, so skip it there.

Signed-off-by: Alejandro Hernández Cordero <ahcorde@gmail.com>

cmake/shiboken_helper.cmake

@@ -24,7 +24,9 @@ set(__PYTHON_QT_BINDING_SHIBOKEN_HELPER_INCLUDED TRUE)
 # In CMake 3.27 and later, FindPythonInterp and FindPythonLibs are deprecated.
 # However, Shiboken2 as packaged in Ubuntu 24.04 still use them, so set CMP0148 to
 # "OLD" to silence this warning.
-cmake_policy(SET CMP0148 OLD)
+if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.27.0")
+  cmake_policy(SET CMP0148 OLD)
+endif()
 find_package(Shiboken2 QUIET)
 if(Shiboken2_FOUND)
   message(STATUS "Found Shiboken2 version ${Shiboken2_VERSION}")