gis/gdal: ogr2ogr malfunctions without XML Parser

[katzlbt (Dr. Thomas)]

ogr2ogr fails to convert XML based input files for lack of a XML parser library built in. The error message by ogr2ogr is cryptic and does not point to the problem.

I strongly suggest to build gdal by default --with-expat ! Expat seems to be used with many other ports so the impact of a default=ON should be low. xerces currently fails to build so expat is the choice.

variant kmlgpx description {Enable XML (KML and GPX) conversions via expat library.} {

depends_lib-append port:expat configure.args-delete --without-expat configure.args-append --with-expat=${prefix}

}