[MacPorts] #59834: Boost: refactor and enhance

[MacPorts]

#59834: Boost: refactor and enhance
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  Reporter:  michaelld    |      Owner:  mascguy
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  boost        |
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Comment (by RJVB):

 Starting (finally!) to migrate to the new boost port infrastructure. 2
 things I noticed:

 - dist_subdir could have been used to store all distfiles in a single
 directory
 - instead of a `cmake_scripts` variant, they could have been provided
 through a subport. That would have made the experimenting easier, and make
 things possible like adding a build conflict for dependents where these
 scripts should NOT be used.

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Ticket URL: <https://trac.macports.org/ticket/59834#comment:45>
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