cmd/compilebench: update list of packages

There's a surprising amount of variety
in the drivers of compilation speed.
It's helpful to have a variety of packages here.
For example, archive/tar exhibits golang/go#19839
much more than the others.

Change-Id: If66b332d63427fb246305cb14cfee9ef450bcdcf
Reviewed-on: https://go-review.googlesource.com/39713
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
1 file changed