[MacPorts] #58646: gcc8 @8.3.0_4 +universal: does not build/install universal libraries

[MacPorts]

#58646: gcc8 @8.3.0_4 +universal: does not build/install universal libraries
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  Reporter:  Ionic      |      Owner:  (none)
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  gcc8 gcc9  |
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Comment (by Ionic):

 OpenBLAS uses Fortran and... I guess that for some reason people want to
 select what compiler to use. For me it's just another dependency, but we
 also have similar setups for, e.g., the `root` ports. Not exposing the
 selection to the user would not help in this case, though, since even when
 only used internally it wouldn't depend on any `libgcc` version directly
 or indirectly.

 Yes, the variant was not automatically switched. But additionally,
 `libgcc9` replaced content installed by `libgcc8`, but nothing pulled in
 the `+universal` variant.

 Installing `OpenBLAS +universal+gcc9` fails in exactly the same way. Even
 though the compilers PG is used, no dependency upon the correct libgcc
 version is added, so no architecture check takes place which would rebuild
 libgcc stuff with `+universal`.

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Ticket URL: <https://trac.macports.org/ticket/58646#comment:7>
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