The Cross Toolchain for the ICnova devices is included within the buildroot. It's being created the first time the image is generated. It contains all the programs needed to create software for the ICnova.
After generation, the toolchain can be found in the directory build_arm/staging_dir/usr/bin. You can use it to create own programs, too. If you move the compilation of your program to project_build_arm/<project>/root it will also be merged into the next image you create and so it will be available on the ICnova.
See also Buildroot directories