package/libxslt: fix build with latest libxml2

Build is broken since bump of libxml2 to version 2.9.11 in commit
a241dcec41 because libxslt calls the
following command "${XML_CONFIG} --libs print" which will return an
error code since
2a357ab99e

Fixes:
 - http://autobuild.buildroot.org/results/47ceb8c24c9ead8a450b7fea3266f760d6b77b4f

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libxslt/0001-Fix-xml2-config-check-in-configure-script.patch

@@ -0,0 +1,31 @@
+From 90c34c8bb90e095a8a8fe8b2ce368bd9ff1837cc Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Fri, 15 Nov 2019 11:53:11 +0100
+Subject: [PATCH] Fix xml2-config check in configure script
+
+A 'print' option has never been supported. After a recent change to
+libxml2, invalid options cause xml2-config to fail.
+
+[Retrieved from:
+https://gitlab.gnome.org/GNOME/libxslt/-/commit/90c34c8bb90e095a8a8fe8b2ce368bd9ff1837cc]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ configure.ac | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/configure.ac b/configure.ac
+index 3da57b18..585b9d7c 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -548,7 +548,7 @@ dnl make sure xml2-config is executable,
+ dnl test version and init our variables
+ dnl
+ 
+-if test "x$LIBXML_LIBS" = "x" && ${XML_CONFIG} --libs print > /dev/null 2>&1
++if test "x$LIBXML_LIBS" = "x" && ${XML_CONFIG} --libs > /dev/null 2>&1
+ then
+     AC_MSG_CHECKING(for libxml libraries >= $LIBXML_REQUIRED_VERSION)
+     XMLVERS=`$XML_CONFIG --version`
+-- 
+GitLab
+

package/libxslt/libxslt.mk

@@ -10,6 +10,8 @@ LIBXSLT_INSTALL_STAGING = YES
 LIBXSLT_LICENSE = MIT
 LIBXSLT_LICENSE_FILES = COPYING
 LIBXSLT_CPE_ID_VENDOR = xmlsoft
+# We're patching configure.ac
+LIBXSLT_AUTORECONF = YES
 
 LIBXSLT_CONF_OPTS = \
 	--with-gnu-ld \