When using esp-idf, files embedding process works little different that current docs suggest

[AgainPsychoX]

See https://docs.platformio.org/en/latest/platforms/espressif32.html#embedding-binary-data (sources at https://github.com/platformio/platformio-docs/blob/develop/frameworks/espidf_extra.rst).

The docs suggest using _binary_src_ prefix (to compensate for src/ folder) in externs for the embedded data labels. Meanwhile (at least for me) generated files and labels do not include the src_ prefix, just _binary_ alone.

The solution might need some refining (and confirmation) I guess. I am not confident with PlatformIO / esp-idf myself, but I am posting it here (as an issue) so maybe other, more knowledgeable people could look at it. Anyway, it works for me ;)