feat(make) add lvgl interface target for micropython (#2529)

* Add lvgl interface target for micropython

* Add indentation to CMakeLists.txt

CMakeLists.txt

@@ -64,14 +64,29 @@ zephyr_library()
         file(GLOB_RECURSE SOURCES src/*.c)
         zephyr_library_sources(${SOURCES})
 
-endif() # CONFIG_LVGL
+    endif(CONFIG_LVGL)
 
 else()
 
     file(GLOB_RECURSE SOURCES ${CMAKE_CURRENT_LIST_DIR}/src/*.c)
-add_library(lvgl STATIC ${SOURCES})
-
     file(GLOB_RECURSE EXAMPLE_SOURCES ${CMAKE_CURRENT_LIST_DIR}/examples/*.c)
+
+    if(MICROPY_DIR)
+        # with micropython, build lvgl as interface library
+        # link chain is: lvgl_interface [lvgl] → usermod_lvgl_bindings [lv_bindings] → usermod [micropython] → firmware [micropython]
+        add_library(lvgl_interface INTERFACE)
+        # ${SOURCES} must NOT be given to add_library directly for some reason (won't be built)
+        target_sources(lvgl_interface INTERFACE ${SOURCES})
+        # Micropython builds with -Werror; we need to suppress some warnings, such as:
+        #
+        # /home/test/build/lv_micropython/ports/rp2/build-PICO/lv_mp.c:29316:16: error: 'lv_style_transition_dsc_t_path_xcb_callback' defined but not used [-Werror=unused-function]
+        # 29316 | STATIC int32_t lv_style_transition_dsc_t_path_xcb_callback(const struct _lv_anim_t * arg0)
+        #       |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+        target_compile_options(lvgl_interface INTERFACE -Wno-unused-function)
+    else(MICROPY_DIR)
+        # without micropython, build lvgl and examples libs normally
+        add_library(lvgl STATIC ${SOURCES})
         add_library(lvgl_examples STATIC ${EXAMPLE_SOURCES})
+    endif(MICROPY_DIR)
 
 endif()