build system: Add idf_component_add_link_dependency function, use for spi_flash overriding

docs/en/api-guides/build-system.rst

@@ -605,6 +605,23 @@ The order of components in the ``BUILD_COMPONENTS`` variable determines other or
 - Order that :ref:`project_include.cmake` files are included into the project.
 - Order that the list of header paths is generated for compilation (via ``-I`` argument). (Note that for a given component's source files, only that component's dependency's header paths are passed to the compiler.)
 
+Adding link-time dependencies
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. highlight:: cmake
+
+The ESP-IDF CMake helper function ``idf_component_add_link_dependency`` adds a link-only dependency between one component and another. In almost all cases, it's better to use the ``PRIV_REQUIRES`` feature in ``idf_component_register`` to create a dependency. However in some cases it's necessary the link-time dependency of another component to this component, i.e. the reverse order to ``PRIV_REQUIRES`` (for example: :doc:`/api-reference/storage/spi_flash_override_driver`).
+
+To make another component depend on this component at link time::
+
+  idf_component_add_link_dependency(FROM other_component)
+
+Place this line after the line with ``idf_component_register``.
+
+It's also possible to specify both components by name::
+
+  idf_component_add_link_dependency(FROM other_component TO that_component)
+
 .. _override_project_config:
 
 Overriding Parts of the Project