SiFive's HiFive1 is an Arduino compatible dev kit featuring the RISC-V Freedom E310 micro-controller.
You can get it at sifive.com.
You can use GNAT FSF riscv64-elf and GPRbuild releases from the Alire project, download here.
A public release of GNAT Studio is also available here.
To build the example, make sure sure you have all the tools in your PATH and run:
$ gprbuild -f -p -P hifive1_example.gpr -XPLATFORM_BUILD=Debug
Follow the instructions in the freedom-e-sdk to flash the example on the board using OpenOCD.