Assuming that ${MICROPY_PORT_DIR}/boards/${MICROPY_BOARD} is equal to
${MICROPY_BOARD_DIR} is not valid, because the latter could point to a path
outside the main MicroPython repository.
Replace this path with the canonical ${MICROPY_BOARD_DIR} so that pins.csv
is correctly located when building against out-of-tree board definitions.
Additionally remove MICROPY_BOARDS_DIR to discourage similar mistakes.
Signed-off-by: Phil Howard <phil@gadgetoid.com>
932f76c6ba