[MacPorts] #70087: plplot fails to build: cc1: error: argument to '-O' should be a non-negative integer, 'g', 's', 'z' or 'fast'

[MacPorts]

#70087: plplot fails to build: cc1: error: argument to '-O' should be a non-
negative integer, 'g', 's', 'z' or 'fast'
---------------------------+--------------------
  Reporter:  barracuda156  |      Owner:  (none)
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.9.3
Resolution:                |   Keywords:
      Port:  plplot        |
---------------------------+--------------------

Comment (by barracuda156):

 I do not see where the source adds this flag btw.

-- 
Ticket URL: <https://trac.macports.org/ticket/70087#comment:1>
MacPorts <https://www.macports.org/>
Ports system for macOS