[MacPorts] #49359: tdom: fix build failure with tcl 8.6

[MacPorts]

#49359: tdom: fix build failure with tcl 8.6
------------------------+---------------------------------
  Reporter:  neumann@…  |      Owner:  ryandesign@…
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.3.4
Resolution:             |   Keywords:  haspatch maintainer
      Port:  tdom       |
------------------------+---------------------------------

Comment (by ryandesign@…):

 I think this will also need to use "github.tarball_from downloads".

-- 
Ticket URL: <https://trac.macports.org/ticket/49359#comment:6>
MacPorts <https://www.macports.org/>
Ports system for OS X