Log Message:
webkit-gtk: add TOOL_DEPENDS on py-expat

Trying to fix
[ 53%] Generating \ 
../../DerivedSources/JavaScriptCore/IntlDateTimeFormatConstructor.lut.h
Traceback (most recent call last):
  File \ 
"/scratch/www/webkit-gtk/work/webkitgtk-2.26.0/Source/JavaScriptCore/disassembler/udis86/ud_itab.py", \ 
line 379, in <module>
    main()
  File \ 
"/scratch/www/webkit-gtk/work/webkitgtk-2.26.0/Source/JavaScriptCore/disassembler/udis86/ud_itab.py", \ 
line 374, in main
    tables = UdOpcodeTables(xml=sys.argv[1])
  File \ 
"/scratch/www/webkit-gtk/work/webkitgtk-2.26.0/Source/JavaScriptCore/disassembler/udis86/ud_opcode.py", \ 
line 326, in __init__
    for insn in self.__class__.parseOptableXML(xml):
  File \ 
"/scratch/www/webkit-gtk/work/webkitgtk-2.26.0/Source/JavaScriptCore/disassembler/udis86/ud_opcode.py", \ 
line 585, in parseOptableXML
    xmlDoc = minidom.parse(xml)
  File "/usr/pkg/lib/python2.7/xml/dom/minidom.py", line 1917, in parse
    from xml.dom import expatbuilder
  File "/usr/pkg/lib/python2.7/xml/dom/expatbuilder.py", line 32, in \ 
<module>
    from xml.parsers import expat
  File "/usr/pkg/lib/python2.7/xml/parsers/expat.py", line 4, in \ 
<module>
    from pyexpat import *
ImportError: No module named pyexpat