Maximum transition time set in a weird manner

[donn]

Description

Typically, if the user does not want to explicitly override the maximum transition time set by the PDK, the synthesis script or the SDC file should just fall back to that provided by the lib files.

OpenLane, on the other hand, attempts to calculate a heuristic of 0.1*$::env(SYNTH_MAX_TRAN)??

Additionally, $::env(SYNTH_MAX_TRAN) is unused in the base.sdc file.

Expected Behavior

If SYNTH_MAX_TRAN is unset, don't set a max transition time. If it is set, use it. Period.

Environment report

Kernel: Linux v6.0.19
Distribution: nixos 22.11
Python: v3.10.9 (OK)
Container Engine: docker v20.10.21 (OK)
OpenLane Git Version: a36049b46a768a6fd956330d5c905900736883b6
pip: INSTALLED
python-venv: INSTALLED
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PDK Version Verification Status: OK
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Git Log (Last 3 Commits)

a36049b4 2023-05-28T15:33:09+03:00 [BOT] Update openroad_app (#1801) - Openlane Bot -  (HEAD -> master, tag: 2023.05.29, upstream/master, fix_max_tr)
5880f358 2023-05-24T17:30:26+03:00 Read multi-corner libs while running resizer and CTS (#1804) - Kareem Farid -  (tag: 2023.05.25)
5ee2232d 2023-05-24T17:21:03+03:00 Update Readme to Include Citation (#1820) - Mohamed Gaber -  ()
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Git Remotes

origin  git@github.com:donn/openlane (fetch)
origin  git@github.com:donn/openlane (push)
upstream        git@github.com:the-openroad-project/openlane (fetch)
upstream        git@github.com:the-openroad-project/openlane (push)

Reproduction material

N/A

Relevant log output

N/A