Unconditionally define add_python_targets for ease of use.

If there is no python interpreter then it will do nothing.

cmake/modules/DunePythonCommonMacros.cmake

@@ -128,17 +128,6 @@ if(Python3_Interpreter_FOUND)
 
     include_directories("${Python3_INCLUDE_DIRS}")
 
-    function(add_python_targets base)
-      include(DuneSymlinkOrCopy)
-      if(PROJECT_SOURCE_DIR STREQUAL PROJECT_BINARY_DIR)
-        message(WARNING "Source and binary dir are the same, skipping symlink!")
-      else()
-        foreach(file ${ARGN})
-          dune_symlink_to_source_files(FILES ${file}.py)
-        endforeach()
-      endif()
-    endfunction()
-
     include(DuneAddPybind11Module)
     message(STATUS "Python bindings enabled")
   endif()
@@ -176,3 +165,17 @@ else()
   )
   set(DUNE_ENABLE_PYTHONBINDINGS OFF)
 endif()
+
+include(DuneSymlinkOrCopy)
+
+function(add_python_targets base)
+  if(Python3_Interpreter_FOUND)
+    if(PROJECT_SOURCE_DIR STREQUAL PROJECT_BINARY_DIR)
+      message(WARNING "Source and binary dir are the same, skipping symlink!")
+    else()
+      foreach(file ${ARGN})
+        dune_symlink_to_source_files(FILES ${file}.py)
+      endforeach()
+    endif()
+  endif()
+endfunction()