make: Create stripped elf binary for aboot

Add rules to create stripped elf binary.

CRs-Fixed: 626209
Change-Id: I1d603c7e371daddc1db6d79f99c6afacd0f31645
diff --git a/make/build.mk b/make/build.mk
index ffbcdc4..262d2e9 100644
--- a/make/build.mk
+++ b/make/build.mk
@@ -39,5 +39,9 @@
 	$(NOECHO)$(OBJCOPY) -I binary -B arm -O elf32-littlearm $(INPUT_TZ_BIN) $(OUTPUT_TZ_BIN)
 endif
 
+$(OUTELF_STRIP): $(OUTELF)
+	@echo generating stripped elf: $@
+	$(NOECHO)$(STRIP) -S $< -o $@
+
 include arch/$(ARCH)/compile.mk