[MacPorts] #38317: silo: upgrade to 4.9

[MacPorts]

#38317: silo: upgrade to 4.9
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  Reporter:  kurtjaeke@…  |      Owner:  macports-tickets@…
      Type:  update       |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  silo         |
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Comment (by ryandesign@…):

 Are you certain that the szip dependency should be added in the +hdf5
 variant? Does silo itself require szip functions, or are they only used
 via hdf5-18's interface to them? hdf5-18 can be compiled with or without
 szip support, via its +szip variant, and the default is off. Can we leave
 it up to the hdf5-18 port to be in charge of whether szip is used, or does
 silo really require hdf5-18 with szip support? If the latter, we might
 want to use the active_variants portgroup to do that.

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Ticket URL: <https://trac.macports.org/ticket/38317#comment:2>
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