[MacPorts] #62124: gcc9 @9.3.0_4 gfortran fails with "ld: library not found for -lSystem" in Big Sur

[MacPorts]

#62124: gcc9 @9.3.0_4 gfortran fails with "ld: library not found for -lSystem" in
Big Sur
------------------------+--------------------
  Reporter:  cquike     |      Owner:  (none)
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.6.4
Resolution:             |   Keywords:  bigsur
      Port:  gcc8 gcc9  |
------------------------+--------------------

Comment (by kencu):

 99.999% chance it is the same problem we have with all the gccs -- the SDK
 moved by a decimal point, and so gcc is broken.

 see this thread <https://lists.macports.org/pipermail/macports-
 dev/2021-January/042775.html>

 We cannot as yet get agreement to build gcc against "MacOSX.sdk" on new
 systems, but  -- we will.

-- 
Ticket URL: <https://trac.macports.org/ticket/62124#comment:2>
MacPorts <https://www.macports.org/>
Ports system for macOS