Con't build external memory files if EMC support is not enabled

configs/open1788/src/Makefile

@@ -40,6 +40,7 @@ CFLAGS += -I$(TOPDIR)/sched
 ASRCS = 
 CSRCS = lpc17_boardinitialize.c lpc17_ssp.c
 
+ifeq ($(CONFIG_LPC17_EMC),y)
 ifeq ($(CONFIG_ARCH_EXTNOR),y)
   CSRCS += lpc17_norinitialize.c
 endif
@@ -51,6 +52,7 @@ endif
 ifeq ($(CONFIG_ARCH_EXTDRAM),y)
   CSRCS += lpc17_sdraminitialize.c
 endif
+endif
 
 ifeq ($(CONFIG_LPC17_LCD),y)
   CSRCS += lpc17_lcd.c