better finding of python extensions

CMakeLists.txt

@@ -90,6 +90,7 @@ if (NOT CMAKE_IMPORT_LIBRARY_PREFIX)
     set(CMAKE_IMPORT_LIBRARY_PREFIX import_)
 endif()
 
+add_subdirectory(third_party)
 
 if (PYCLINGODL_ENABLE)
     if(NOT PYCLINGODL_ENABLE STREQUAL "pip" AND (CMAKE_VERSION VERSION_GREATER "3.15.0" OR CMAKE_VERSION VERSION_EQUAL "3.15.0"))
@@ -116,9 +117,14 @@ if (PYCLINGODL_ENABLE)
         if (PYCLINGODL_ENABLE STREQUAL "require" OR PYCLINGODL_ENABLE STREQUAL "pip")
             set(_args ${_args} REQUIRED)
         endif()
-        find_package(PythonInterp ${_args})
-        find_package(PythonLibs ${_args})
+        if (PYCLINGODL_ENABLE STREQUAL "pip")
+            find_package(PythonExtensions ${_args})
+        else()
+            find_package(PythonInterp ${_args})
+            find_package(PythonLibs ${_args})
+        endif()
         set(Python_EXECUTABLE "${PYTHON_EXECUTABLE}")
+        set(Python_VERSION_MAJOR "${PYTHON_VERSION_MAJOR}")
         if (PYTHONLIBS_FOUND)
             add_library(Python::Python INTERFACE IMPORTED)
             add_library(Python::Module INTERFACE IMPORTED)
@@ -135,7 +141,6 @@ if (PYCLINGODL_ENABLE)
     endif()
 endif()
 
-add_subdirectory(third_party)
 if (PYCLINGODL_ENABLE STREQUAL "pip")
     if (NOT CLINGODL_BUILD_SHARED)
         message(FATAL_ERROR "building against the pip package requires CLINGODL_BUILD_SHARED.")