Use build fingerprint from file

Improve incremental ninja builds by keeping the command line the same
across builds.

Change-Id: Iedbaa40c9f816f91afc8f073a9ed7f9ffd5d9a53
diff --git a/Android.mk b/Android.mk
index 487ae4d..2d5dc45 100644
--- a/Android.mk
+++ b/Android.mk
@@ -342,7 +342,7 @@
 include $(BUILD_SYSTEM)/base_rules.mk
 $(LOCAL_BUILT_MODULE): $(built_sepolicy) $(built_pc) $(built_fc) $(built_sc) $(built_svc)
 	@mkdir -p $(dir $@)
-	$(hide) echo -n $(BUILD_FINGERPRINT) > $@
+	$(hide) echo -n $(BUILD_FINGERPRINT_FROM_FILE) > $@
 
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