SiFive's HiFive1 is an Arduino compatible dev kit featuring the RISC-V Freedom E310 micro-controller.
You can get it at sifive.com.
How to setup the Ada development environment for the HiFive1
GNAT Community now comes with HiFive1 support built-in. So you only need to download the RISC-V32 ELF and the native package from here.
Building the example
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.