666b1b68a7
For non-incremental builds on Unix, currently all the thread names look like `opt regex.f10ba03eb5ec7975-cgu.0`. But they are truncated by `pthread_setname` to `opt regex.f10ba`, hiding the numeric suffix that distinguishes them. This is really annoying when using a profiler like Samply. This commit changes these thread names to a form like `opt cgu.0`, which is much better.