handle OR
  core-$(CONFIG_IA64_DIG)         += arch/ia64/dig/
  core-$(CONFIG_IA64_DIG_VTD)     += arch/ia64/dig/
  core-$(CONFIG_IA64_GENERIC)     += arch/ia64/dig/
  core-$(CONFIG_IA64_HP_ZX1)      += arch/ia64/dig/
tracking the tree?
Note: so every makefile is opened only once
The result: two lines?

handle if/else construct in makefiles



