By default we ship clpeak on ChromeOS test builds so you do not need to build the binaries yourself simply run /usr/local/opencl/clpeak you should see output similar to this : https://github.com/krrishnarraj/clpeak#sample

If you wish to build once you have a ChromeOS checkout and chroot working just follow these simple instructions:

build

emerge-${BOARD} clpeak

deploy

cros deploy clpeak

run

ssh /usr/local/opencl/clpeak