File building-docs-once-is-enough.patch of Package k3b

--- k3b-2.0.3.orig/CMakeLists.txt	2014-11-04 19:43:47.000000000 +0100
+++ k3b-2.0.3/CMakeLists.txt	2015-10-11 15:11:18.653146229 +0200
@@ -350,6 +350,3 @@ macro_display_feature_log()
 
 include(MacroOptionalAddSubdirectory)
 macro_optional_add_subdirectory( po )
-
-include(MacroOptionalAddSubdirectory)
-macro_optional_add_subdirectory( doc )