ZyklonB: don't look for plugins in /usr/lib

It's quite unlikely that this project will ever see compiled plugins.

config.h.in

@@ -2,7 +2,6 @@
 #define CONFIG_H
 
 #define PROGRAM_VERSION "${project_version}"
-#define LIBDIR "${CMAKE_INSTALL_FULL_LIBDIR}"
 
 #cmakedefine HAVE_READLINE
 #cmakedefine HAVE_EDITLINE

zyklonb.c

@@ -1019,7 +1019,6 @@ plugin_resolve_relative_filename (const char *filename)
 {
 	struct strv paths = strv_make ();
 	get_xdg_data_dirs (&paths);
-	strv_append (&paths, LIBDIR);  // Legacy, we do not compile any plugins
 	char *result = resolve_relative_filename_generic
 		(&paths, PROGRAM_NAME "/plugins/", filename);
 	strv_free (&paths);