[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
------------------------+--------------------
  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):

 ... yes, right. I didn't check that.

 So I guess the `gcc` ports aren't really broken, but with all that stuff,
 how do we make sure that a compatible `libgcc` version is installed?

 Look at OpenBLAS: I previously installed it with the (then default)
 `+gcc8` variant and it did work back then, because `libgcc8` was a "full"
 port and installed with `+universal` due to some dependency. That worked
 fine. Recently, `libgcc8` was replaced with a stub port and `libgcc9` is
 now providing the libraries needed. That's fine, because GCC and its
 libraries are generally forward compatible (and if they aren't, the soname
 changes). However, nothing pulled in the `+universal` variant when
 `libgcc9` was installed. Boom, no more `+universal` `libgfortran.5.dylib`,
 OpenBLAS `+universal` fails.

 I *can* fix that situation manually by rebuilding `libgcc9` `+universal`,
 but that isn't exactly a great solution for other users. Fixing the port
 is difficult because the actual `libgcc` port that provides a specific
 library is not easy to determine. For instance, just because `libgcc8` is
 a stub port on my system that has been "replaced" by the contents of
 `libgcc9`, this needs not be true for other systems - i.e., old systems
 that can't use `libgcc9` retain `libgcc8` as a "full" port with the
 original contents.

-- 
Ticket URL: <https://trac.macports.org/ticket/58646#comment:4>
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