Log hashes per step

[oharboe]

Review only the most recent commit, builds on #3297

Example output:

$ make do-2_1_floorplan
[deleted]
Design area 650 u^2 57% utilization.
Elapsed time: 0:00.28[h:]min:sec. CPU time: user 0.29 sys 0.12 (147%). Peak memory: 101020KB.
Log                        Elapsed/s Peak Memory/MB  sha1sum .odb [0:20)
2_1_floorplan                      0             98 50eac5062cd153c214bc

In the bazel-orfs use-case, the .odb files are not all present in the finish step, so log as we go along in addition to the finish step.

A little bit more verbose than I could have wished for, but it does the job. Refine later, possibly.

[oharboe]

@maliberty merge manually? asap7 cva6 timeouts...