Only link to libxml2, addresses https://trac.macports.org/ticket/68704

--- configure.ac.orig
+++ configure.ac
@@ -281,7 +281,7 @@
 
 
 dnl Extract the linker and include flags
-XML2_LDFLAGS=`$XML2CONFIG --libs`
+XML2_LDFLAGS=`$XML2CONFIG --libs --dynamic`
 XML2_CPPFLAGS=`$XML2CONFIG --cflags`
 
 dnl Extract the version