Initial commit of microbenchmark tool.

"Hello World"-style example of the microbenchmark tool that pipecleans
the cmake-build.

Signed-off-by: Jens Elofsson <jens.elofsson@arm.com>

Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Reviewed-by: Felix Johnny Thomasmathibalan <felixjohnny.thomasmathibalan@arm.com>
Approved-by: Jakub Sujak <jakub.sujak@arm.com>
Approved-by: Anton Bondarenko <anton.bondarenko@arm.com>