So that files like python_logging.conf ends up in $EPREFIX/etc.
https://bugs.gentoo.org/show_bug.cgi?id=598537

Index: catkin-0.7.4/cmake/all.cmake
===================================================================
--- catkin-0.7.4.orig/cmake/all.cmake
+++ catkin-0.7.4/cmake/all.cmake
@@ -163,7 +163,7 @@ unset(_CATKIN_CURRENT_PACKAGE)
 
 # set global install destinations
 set(CATKIN_GLOBAL_BIN_DESTINATION bin)
-set(CATKIN_GLOBAL_ETC_DESTINATION etc)
+set(CATKIN_GLOBAL_ETC_DESTINATION ../etc)
 set(CATKIN_GLOBAL_INCLUDE_DESTINATION include)
 set(CATKIN_GLOBAL_LIB_DESTINATION ${CMAKE_INSTALL_LIBDIR})
 set(CATKIN_GLOBAL_LIBEXEC_DESTINATION libexec)