libxml2: Apply ABI breaking patch from Chromium needed for libxslt CVE fixes

pkgs/development/libraries/libxml2/default.nix

@@ -51,6 +51,15 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-J3KUyzMRmrcbK8gfL0Rem8lDW4k60VuyzSsOhZoO6Eo=";
   };
 
+  patches = [
+    # Unmerged ABI-breaking patch required to fix the following security issues:
+    # - https://gitlab.gnome.org/GNOME/libxslt/-/issues/139
+    # - https://gitlab.gnome.org/GNOME/libxslt/-/issues/140
+    # See also https://gitlab.gnome.org/GNOME/libxml2/-/issues/906
+    # Source: https://github.com/chromium/chromium/blob/4fb4ae8ce3daa399c3d8ca67f2dfb9deffcc7007/third_party/libxml/chromium/xml-attr-extra.patch
+    ./xml-attr-extra.patch
+  ];
+
   strictDeps = true;
 
   nativeBuildInputs = [

pkgs/development/libraries/libxml2/xml-attr-extra.patch

@@ -0,0 +1,20 @@
+diff --git a/include/libxml/tree.h b/include/libxml/tree.h
+index e5a8fb709471f..7819d5819b427 100644
+--- a/include/libxml/tree.h
++++ b/include/libxml/tree.h
+@@ -454,6 +454,7 @@ struct _xmlAttr {
+     xmlAttributeType atype;     /* the attribute type if validating */
+     void            *psvi;	/* for type/PSVI information */
+     struct _xmlID   *id;        /* the ID struct */
++    unsigned int     extra;     /* extra data for XPath/XSLT */
+ };
+ 
+ /**
+@@ -592,6 +593,7 @@ struct _xmlDoc {
+ 				   document */
+     int             properties;	/* set of xmlDocProperties for this document
+ 				   set at the end of parsing */
++    unsigned int    extra;      /* extra data for XPath/XSLT */
+ };
+ 
+