why Eclipse 4.5.2 Release Build: 4.5.2 no delta pack for download now?
Since Eclipse 4.5 delta packs are no longer being created.
The preferred way to do multi-platform builds is now to set your target platform to the appropriate Eclipse repository.
It is also possible to build your own delta pack. See here for more details on the options. In particular note that Eclipse Tycho is now the recommended way to do builds.