Merge: Fast benches

Last week benches shows some failures on some options due to recent commits.

This PR add a `--fast --fast` option that test only `hello_world` so it could be used in continuous integration to test the various meaningful combination of compiling options.

Moreover, the script is simplified to be more simple to use and extends with new options or combination of options,

Pull-Request: #1217
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>