[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):

 so the simplest thing to do is make a symlink from MacOSX11.0.sdk to
 MacOSX11.1.sdk and that gets you fixed for right now.

 To fix this correctly, remove that symlink if you make it, and rebuild gcc
 from source on your local machine, like this:
 {{{
 sudo port -v -s install gcc9
 }}}

 and btw, gcc10 is available if that might be better. It probably also
 needs an SDK rebuild, sorry.

 we are trying to get to a compromise on how we'll fix this properly,
 hopefully without too much more time going by.

-- 
Ticket URL: <https://trac.macports.org/ticket/62124#comment:8>
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