Fix man page installation location

Author: jp-bennett

CMakeLists.txt

@@ -87,7 +87,7 @@ add_custom_target(man ALL DEPENDS ${MAN_FILES})
   install(TARGETS fwknop-gui DESTINATION bin)
   install(PROGRAMS fwknop-gui.desktop DESTINATION share/applications)
   install(FILES fwknop-gui.png DESTINATION share/pixmaps)
-  INSTALL(FILES ${CMAKE_CURRENT_BINARY_DIR}/fwknop-gui.8 DESTINATION ${CMAKE_INSTALL_PREFIX}/man/man1)
+  INSTALL(FILES fwknop-gui.8 DESTINATION share/man/man8)
 endif()
 if(IS_WIN32)
   include_directories( ${LIBQRENCODE_INCLUDE_DIR} )