[MacPorts] #45302: mpv: update to 0.6.0

[MacPorts]

#45302: mpv: update to 0.6.0
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  Reporter:  marek.krolikowski@…  |      Owner:  ionic@…
      Type:  update               |     Status:  new
  Priority:  Normal               |  Milestone:
 Component:  ports                |    Version:  2.3.1
Resolution:                       |   Keywords:  haspatch
      Port:  mpv                  |
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Comment (by marek.krolikowski@…):

 It's my first time patching portfile.

 1. Reseting revision is no problem
 2. This code must be run right after build, I found the "post-build"
 method. How can I achieve this inside variant declaration?

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Ticket URL: <https://trac.macports.org/ticket/45302#comment:2>
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