make: add provision to get CFLAGS for LE

For Rocko, gcc version is upgraded to 6.4, which adds new flags by default
which are causing issues in LK. Inorder to pass the dependent CFLAGS
LKLE_CFLAGS variable is added which appends all flags passed by yocto.

Change-Id: I171a8d1c8f18069fd6bb19ccbf5ad221a8b99f5d
diff --git a/makefile b/makefile
index a1b091e..156ebeb 100644
--- a/makefile
+++ b/makefile
@@ -50,7 +50,7 @@
 endif
 
 INCLUDES := -I$(BUILDDIR) -Iinclude
-CFLAGS := -O2 -g -fno-builtin -finline -W -Wall -Wno-multichar -Wno-unused-parameter -Wno-unused-function -include $(CONFIGHEADER)
+CFLAGS := -O2 -g -fno-builtin -finline -W -Wall -Wno-multichar -Wno-unused-parameter -Wno-unused-function $(LKLE_CFLAGS) -include $(CONFIGHEADER)
 #CFLAGS += -Werror
 ifeq ($(EMMC_BOOT),1)
   CFLAGS += -D_EMMC_BOOT=1