citrix_workspace: add 20.09.0

ChangeLog: https://docs.citrix.com/en-us/citrix-workspace-app-for-linux/whats-new.html#whats-new-in-2009

Also removed 19.12.0 which will be out of maintenance in April 2021
which is still within the lifetime of 20.09.

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

@@ -149,6 +149,10 @@ stdenv.mkDerivation rec {
     sed -i -e 's,^ANSWER="",ANSWER="$INSTALLER_YES",g' -e 's,/bin/true,true,g' ./linuxx64/hinst
     ${stdenv.shell} linuxx64/hinst CDROM "$(pwd)"
 
+    if [ -f "$ICAInstDir/util/setlog" ]; then
+      chmod +x "$ICAInstDir/util/setlog"
+      ln -sf "$ICAInstDir/util/setlog" "$out/bin/citrix-setlog"
+    fi
     ${mkWrappers wrapLink toWrap}
     ${mkWrappers wrap [ "PrimaryAuthManager" "ServiceRecord" "AuthManagerDaemon" "util/ctxwebhelper" ]}