Add an idempotency test

[oharboe]

Description

Add this test to ORFS.

To do so, requires:

• Add write_spec -date_zero option to enable idempotent .spef files OpenROAD#5526 and use from within ORFS
• figure out why .gds files differ with the test below. Probably there are some date fields within .gds files that could be set to a fixed date or omitted.

#!/bin/bash
#
# Run a smoketest with two builds and check for identical results
set -ue -o pipefail

cd "$(dirname "$0")/.."
. ../env.sh

make FLOW_VARIANT=a
# Pile on as many options as possible that should not affect the result
make SKIP_REPORT_TIMING=1 FLOW_VARIANT=b
diff -r results/nangate45/gcd/a/ results/nangate45/gcd/b/

Suggested Solution

Solve the non-idempotency problems and add a CI test which exercises all options that should have no effect on result in an A/B test.

Additional Context

No response