I can't actually run your harness. I tried the instructions, but I got build errors, probably because I don't have all the regex engines installed. It really should be possible to run the benchmarks on a subset of regex engines.
[x] I tried the instructions, but I got build errors [..]
[x] It really should be possible to run the benchmarks on a subset of regex engines.
The issue is part from the feedback of https://github.com/rust-lang/regex/issues/350