Updated for openclonk-6.0, based on this patch:
  From: Julian Ospald <hasufell@gentoo.org>
  Date: Thu Feb  6 19:58:45 UTC 2014
  Subject: make paths modifiable

--- openclonk-release-6.0-src.orig/CMakeLists.txt
+++ openclonk-release-6.0-src/CMakeLists.txt
@@ -42,6 +42,16 @@
 	set(${_var} "${_string}" PARENT_SCOPE)
 endfunction()
 
+
+############################################################################
+# User selectable paths
+############################################################################
+set(INSTALL_BINDIR "bin/" CACHE PATH "Binary install destination")
+set(INSTALL_GAMES_BINDIR "games/bin" CACHE PATH "Games binary install destination")
+set(INSTALL_DATAROOTDIR "share/" CACHE PATH "Data root install destination")
+set(INSTALL_DATADIR "${INSTALL_DATAROOTDIR}" CACHE PATH "Data install destination")
+
+
 ############################################################################
 # User selectable options
 ############################################################################
@@ -1212,10 +1222,16 @@
 # Assemble compiler flags
 ############################################################################
 if(UNIX)
+	if(NOT IS_ABSOLUTE "${INSTALL_DATADIR}")
+		set(ABSOLUTE_INSTALL_DATADIR "${CMAKE_INSTALL_PREFIX}/${INSTALL_DATADIR}")
+	else()
+		set(ABSOLUTE_INSTALL_DATADIR "${INSTALL_DATADIR}")
+	endif()
+
 	# Don't put this into CMAKE_CXX_FLAGS because otherwise it is cached,
 	# and when the path is changed both the old and new definition appears
 	# in the list of flags.
-	add_definitions("-DOC_SYSTEM_DATA_DIR=\"${CMAKE_INSTALL_PREFIX}/share/games/openclonk\"")
+	add_definitions("-DOC_SYSTEM_DATA_DIR=\"${ABSOLUTE_INSTALL_DATADIR}/openclonk\"")
 endif()
 if(OC_CXX_FLAGS)
 	list(REMOVE_DUPLICATES OC_CXX_FLAGS)
@@ -1537,7 +1553,7 @@
 			DEPENDS "${native_c4group}"
 			VERBATIM
 		)
-		install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${group} DESTINATION share/games/openclonk)
+		install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${group} DESTINATION "${INSTALL_DATADIR}/openclonk")
 	endif()
 endforeach()
 
@@ -1546,13 +1562,13 @@
 	add_dependencies(data groups)
 	
 	# Install new files
-	install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/openclonk.desktop DESTINATION share/applications)
+	install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/openclonk.desktop DESTINATION "${INSTALL_DATAROOTDIR}/applications")
 	# Update the MIME cache -- this makes the clonk:// protocol handler actually work
 	install(CODE "execute_process(COMMAND update-desktop-database)")
 
 	# Install binaries
-	install(TARGETS openclonk DESTINATION games)
-	install(TARGETS c4group DESTINATION bin)
+	install(TARGETS openclonk DESTINATION "${INSTALL_GAMES_BINDIR}")
+	install(TARGETS c4group DESTINATION "${INSTALL_BINDIR}")
 else()
 	install(TARGETS openclonk
 		BUNDLE DESTINATION .