Fixes building with sys-libs/ncurses[tinfo]

--- a/cmake/Modules/FindCurses6.cmake	2014-09-25 16:32:20.000000000 +0400
+++ b/cmake/Modules/FindCurses6.cmake	2014-09-25 16:33:16.000000000 +0400
@@ -11,11 +11,12 @@
   FIND_LIBRARY(CURSES6_TINFO_LIBRARY NAMES tinfo PATHS ${path}/ncurses6 ${path} NO_DEFAULT_PATH)
 ENDFOREACH()
 
-SET(CURSES6_LIBRARIES ${CURSES6_NCURSESW_LIBRARY} ${CURSES6_PANELW_LIBRARY})
 # tinfo is optional (in 12.1 is not there)
-IF(${CURSES6_TINFO_LIBRARY})
-  SET(CURSES6_LIBRARIES "${CURSES6_LIBRARIES} ${CURSES6_TINFO_LIBRARY}")
-ENDIF(${CURSES6_TINFO_LIBRARY})
+IF(NOT ${CURSES6_TINFO_LIBRARY} STREQUAL "CURSES6_TINFO_LIBRARY-NOTFOUND")
+  SET(CURSES6_LIBRARIES ${CURSES6_NCURSESW_LIBRARY} ${CURSES6_PANELW_LIBRARY} ${CURSES6_TINFO_LIBRARY})
+ELSE()
+  SET(CURSES6_LIBRARIES ${CURSES6_NCURSESW_LIBRARY} ${CURSES6_PANELW_LIBRARY})
+ENDIF()
 
 FIND_PATH(CURSES6_INCLUDE_DIR ncurses.h PATH_SUFFIXES ncurses6)