libtt/benchmark: Write out results to a CSV file (as well as stdio)
libtt/benchmark: Write out results to a CSV file (as well as stdio)

This is primarily to test interfaces for continuous integration.

Signed-off-by: Daniel Thompson <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@redfelineninja.org.uk>

daniel-thompson/tintamp,daniel-thompson/tintamp,daniel-thompson/tintamp