Use only the value of WITH_KDE to determine whether to build config_kde.

See the changes in patch-libproxy_cmake_modules_config__kde.cmk for more
information.
--- libproxy/cmake/modules.cmk.orig	2016-01-18 19:41:03 UTC
+++ libproxy/cmake/modules.cmk
@@ -32,7 +32,7 @@ px_module(config_envvar            "${EN
 px_module(config_sysconfig         "${SYSCONFIG_FOUND}" 1)
 px_module(config_gnome             "${GNOME2_FOUND}" 0)
 px_module(config_gnome3            "${GNOME3_FOUND}" 0)
-px_module(config_kde               "${KDE_FOUND}"    0)
+px_module(config_kde               "${WITH_KDE}"     0)
 px_module(config_macosx            "${SC_FOUND}"     1       ${SC_LIBRARIES} ${CF_LIBRARIES})
 px_module(config_w32reg            "${WIN32}"        1)
 px_module(ignore_domain            1                 1)