Configure the board:
$ ./tools/configure.sh esp32c3-devkit:nsh
Compile:
$ make
Convert the NuttX ELF file:
$ esptool.py --chip esp32-c3 elf2image --flash_mode dio --flash_size 4MB -o ./nuttx.bin nuttx
Put the board in bootloader mode (press and hold Boot button and click on RST button, release Boot button)
Flash it:
$ sudo esptool.py --chip esp32-c3 --port /dev/ttyUSB0 --baud 921600 write_flash 0x10000 nuttx.bin