Use sha256 when zipping target_files

similar to general-tests.mk, this will avoid recomputing sha256 when
uploading target files to RBE.

Test: presubmit
Bug: 316952196
Change-Id: I879214ac79f5c269f337fafcede8513c1e90e60e
diff --git a/core/Makefile b/core/Makefile
index 4a1cda1..3f0da8b 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -6750,7 +6750,7 @@
 
 $(BUILT_TARGET_FILES_PACKAGE): $(BUILT_TARGET_FILES_DIR)
 	@echo "Packaging target files: $@"
-	$(hide) $(SOONG_ZIP) -d -o $@ -C $(zip_root) -r $@.list
+	$(hide) $(SOONG_ZIP) -d -o $@ -C $(zip_root) -r $@.list -sha256
 
 .PHONY: target-files-package
 target-files-package: $(BUILT_TARGET_FILES_PACKAGE)