esp32: preserve non-CONFIG_ build args when using --custom-board-path

[thatbudakguy]

Summary

build_sdkconfig() in builder/esp32.py returns an empty list whenever custom_board_path is set, discarding all extra build args passed to compile() -- not just the CONFIG_ ones. This drops GEN_SCRIPT and FROZEN_MANIFEST, which the rest of the build needs regardless of whether a custom board is used.

Without GEN_SCRIPT, cmake evaluates $ENV{GEN_SCRIPT} as empty when generating LVGL bindings, and looks for gen/_api_gen_mpy.py instead of gen/python_api_gen_mpy.py:

CMake Error at ext_mod/lvgl/micropython.cmake:45 (message):
  Failed to generate .../lv_mp.c
.../bin/python: can't open file '.../lvgl_micropython/gen/_api_gen_mpy.py': [Errno 2] No such file or directory

This breaks the ESP32 build for any project using --custom-board-path (reproduced with a fresh custom board pointing at an M5Stack Tough).

Fix

Only the CONFIG_* args are meant to be skipped for custom boards, since those boards supply their own sdkconfig fragment via sdkconfig.board. The other build args (GEN_SCRIPT, FROZEN_MANIFEST, etc.) should still be forwarded.

Test plan

• Reproduced the failure on a clean ESP32 build with --custom-board-path
• Applied this fix and confirmed the build proceeds past LVGL binding generation and completes successfully end to end (full firmware compiles and links)

[kdschlosser]

the only one we should have to worry about preserving is GEN_SCRIPT. the rest of them can be ignored as they are able to be set in the files that are located in the custom boards directory.

[thatbudakguy]

Should we just hardcode it to:

return ['GEN_SCRIPT']

?

[kdschlosser]

I have to look at the code again to see exactly what is being done. I don't remember where the genscript is being injected and where the block is occurring at.

[kdschlosser]

ok the first location is to change here so it reads

            ${Python3_EXECUTABLE} ${BINDING_DIR}/gen/python_api_gen_mpy.py ${LV_CFLAGS} --output=${CMAKE_BINARY_DIR}/lv_mp.c --include=${BINDING_DIR}/lib --include=${BINDING_DIR}/lib/lvgl --board=$ENV{LV_PORT} --module_name=lvgl --module_prefix=lv --metadata=${CMAKE_BINARY_DIR}/lv_mp.c.json --header_file=${LVGL_DIR}/lvgl.h

[kdschlosser]

the line here can be removed

then change the code here to read

args = build_sdkconfig(*args)
args.append(f'FROZEN_MANIFEST="{SCRIPT_DIR}/build/manifest.py"')

and that should fix the issue.

[anotherdoesnm]

Planned to report issue with $GEN_SCRIPT but seems you're already solved it, just not merged

[thatbudakguy]

@kdschlosser I've updated with your changes.

[anotherdoesnm]

@thatbudakguy i got lvgl_micropython working without this config so don't sure it's still actual