citrix-workspace: fix libxml2 build incompatibility

Breaking ABI change for libxml2 recently, need to override to use
supported libxml version.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

pkgs/applications/networking/remote/citrix-workspace/generic.nix

@@ -55,6 +55,7 @@
   libsecret,
   libcanberra-gtk3,
   sane-backends,
+  fetchurl,
 
   homepage,
   version,
@@ -87,6 +88,14 @@ let
     '';
   };
 
+  libxml2' = libxml2.overrideAttrs rec {
+    version = "2.13.8";
+    src = fetchurl {
+      url = "mirror://gnome/sources/libxml2/${lib.versions.majorMinor version}/libxml2-${version}.tar.xz";
+      hash = "sha256-J3KUyzMRmrcbK8gfL0Rem8lDW4k60VuyzSsOhZoO6Eo=";
+    };
+  };
+
 in
 
 stdenv.mkDerivation rec {
@@ -157,7 +166,7 @@ stdenv.mkDerivation rec {
     libsecret
     libsoup_2_4
     libvorbis
-    libxml2
+    libxml2'
     llvmPackages.libunwind
     libgbm
     nspr