AndroidBoot.mk, makefile: Add support to enable verified boot

Add makefile support to enable verified boot

Change-Id: Ic994485ff09b35af65907c6eb4e9a5ce32215def
diff --git a/makefile b/makefile
index 4f8f53e..6532fce 100644
--- a/makefile
+++ b/makefile
@@ -95,6 +95,14 @@
 # Useful for header files that may be included by one or more source files.
 SRCDEPS := $(CONFIGHEADER)
 
+ifeq ($(VERIFIED_BOOT),1)
+  DEFINES += VERIFIED_BOOT=1
+  DEFINES += _SIGNED_KERNEL=1
+  ifeq ($(DEFAULT_UNLOCK),true)
+    DEFINES += DEFAULT_UNLOCK=1
+  endif
+endif
+
 # these need to be filled out by the project/target/platform rules.mk files
 TARGET :=
 PLATFORM :=