I have also tried with raw open of unistd.h and fcntl.h and the docker image says that undefined reference to open

This is a simple microcontroller. It's not a Linux OS. You don't have any system functions on chip. You create a file like

la_test1.c

and use the RISCV gcc toolchain to compile a hex file that can used in a verilog testbench like it's loaded onto an SPI flash chip that is attached to the Caravel chip and is read by the microcontroller on startup.

Ok, thank you. I will think a another way to do what I have in mind