Use pkg-config for the libxml2 dependency, not the -config script.

Upstream-Status: Pending

RP 2014/5/22

Index: libarchive-3.1.2/configure.ac
===================================================================
--- libarchive-3.1.2.orig/configure.ac	2013-02-09 17:23:03.000000000 +0000
+++ libarchive-3.1.2/configure.ac	2014-05-13 15:26:45.446499108 +0000
@@ -329,10 +329,10 @@
   AS_HELP_STRING([--without-expat], [Don't build support for xar through expat]))
 
 if test "x$with_xml2" != "xno"; then
-  AC_PATH_PROG([XML2_CONFIG], [xml2-config],, [${PATH}])
-  if test "x$XML2_CONFIG" != "x"; then
-    CPPFLAGS="${CPPFLAGS} `${XML2_CONFIG} --cflags`"
-    LIBS="${LIBS} `${XML2_CONFIG} --libs`"
+  PKG_CHECK_MODULES(PKG_XML2, [libxml-2.0],,)
+  if test "x$PKG_XML2_CFLAGS" != "x"; then
+    CPPFLAGS="${CPPFLAGS} ${PKG_XML2_CFLAGS}"
+    LIBS="${LIBS} ${PKG_XML2_LIBS}"
     AC_CHECK_LIB(xml2,xmlInitParser,[true],AC_MSG_FAILURE(Missing xml2 library))
   else
     AC_CHECK_LIB(xml2,xmlInitParser)