[MacPorts] #59486: gdal: add libxml2 dependency

[MacPorts]

#59486: gdal: add libxml2 dependency
------------------------+----------------------
 Reporter:  ryandesign  |      Owner:  Veence
     Type:  defect      |     Status:  assigned
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.6.2
 Keywords:              |       Port:  gdal
------------------------+----------------------
 Looks like gdal links with libxml2 but does not declare a dependency on
 it.

-- 
Ticket URL: <https://trac.macports.org/ticket/59486>
MacPorts <https://www.macports.org/>
Ports system for macOS