Move dune_python_install_package to python subdirectory

This reduces the number of redundant reruns of the env installation.

CMakeLists.txt

@@ -24,11 +24,6 @@ add_subdirectory(share)
 # if Python bindings are enabled, include necessary sub directories.
 if(DUNE_ENABLE_PYTHONBINDINGS)
   add_subdirectory(python)
-  dune_python_install_package(
-    PATH "python"
-    DEPENDS _common _typeregistry
-    CMAKE_METADATA_FILE dune/common/metadata.cmake
-  )
 endif()
 
 # finalize the dune project, e.g. generating config.h etc.

python/CMakeLists.txt

@@ -3,3 +3,9 @@ add_subdirectory(dune)
 configure_file(MANIFEST.in MANIFEST.in)
 configure_file(setup.py.in setup.py)
 configure_file(pyproject.toml.in pyproject.toml)
+
+dune_python_install_package(
+  PATH "."
+  DEPENDS _common _typeregistry
+  CMAKE_METADATA_FILE dune/common/metadata.cmake
+)