The libretiny upload path on `upload_program` SERIAL dispatch re-invokes
PlatformIO (`pio run -t upload -t nobuild`), which needs a full build
tree and `platformio.ini`. That makes it incompatible with a dashboard
that only has prebuilt artifacts.
Bypass PlatformIO for the libretiny+SERIAL+--prebuilt-dir case by calling
`ltchiptool flash write -d <port> <firmware.uf2>` directly. The .uf2
encodes the chip family in its header so no extra config is needed.
ltchiptool ships with the libretiny PlatformIO platform under
~/.platformio/penv/.libretiny/bin/ltchiptool; `get_ltchiptool_path()`
prefers PATH first (pip install ltchiptool) and falls back to the
PlatformIO penv. Without --prebuilt-dir the existing PlatformIO path
remains in place, so this is purely additive.
Issue: esphome/device-builder#572
J. Nick Koston
b8336cddf2