include/linux/compile.h is a generated file, only init/Makefile knows 
about it - including it outside of init/* will cause trouble on
parallel builds.

Also, when compile.h already exists when 'make dep' is run, that'll pick
up a dependency on $(TOPDIR)/include/linux/compile.h. So init/Makefile
needs to tell make that this is actually the same file as 
../include/linux.compile.h