[MacPorts] #41554: gsl: enable avx-optimized compilation

[MacPorts]

#41554: gsl: enable avx-optimized compilation
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  Reporter:  nicos@…      |      Owner:  dtakahashi42@…
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  haspatch
      Port:  gsl          |
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Comment (by nicos@…):

 Sure, I did not include an additional variant because there was not any
 for clang, but it is indeed definitively better.

 One thing is that a gcc48 variant has been recently added, which should
 probably be added if the conditional.

 Another thing, which I wanted to propose to include, although it was not
 greatly written, was the default case, for which no flags are set for now.
 In particular, the latest apple clang (>= 5.0) also can handle avx
 instructions.

 I include a new diff which contains these changes, along with your
 previous modifications.

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Ticket URL: <https://trac.macports.org/ticket/41554#comment:3>
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