[MacPorts] #70367: dia fails to link: Undefined symbols: "_png_get_header_ver"

[MacPorts]

#70367: dia fails to link: Undefined symbols: "_png_get_header_ver"
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  Reporter:  barracuda156  |      Owner:  (none)
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.9.3
Resolution:                |   Keywords:
      Port:  dia           |
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Comment (by barracuda156):

 Replying to [comment:1 ryandesign]:

 Well, generated makefile has no trace of `-lpng`, so that is why it is not
 passed, but I have no idea what goes wrong and how to find it out.

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Ticket URL: <https://trac.macports.org/ticket/70367#comment:3>
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