Support for probing

[iFrostizz]

I'm currently using cargo-flamegraph to generate a flamegraph for a benchmark.
The issue is that the runtime of the setup of the bench is so huge compared to the actual bench, which makes the part that matter invisible since it's too small as a comparison.
I'm aware of the --min-width flag but it doesn't seem to help.

[djc]

If you're on Linux, I suggest using perf directly and passing its output to flamegraph.