fix imgdiff/bsdiff dependencies

These should be regular dependencies, not order-only ones.
diff --git a/core/Makefile b/core/Makefile
index 656a663..da5b4c6 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -651,8 +651,8 @@
 RECOVERY_FROM_BOOT_PATCH := $(intermediates)/recovery_from_boot.p
 $(RECOVERY_FROM_BOOT_PATCH): $(INSTALLED_RECOVERYIMAGE_TARGET) \
                              $(INSTALLED_BOOTIMAGE_TARGET) \
-			     | $(HOST_OUT_EXECUTABLES)/imgdiff \
-	                       $(HOST_OUT_EXECUTABLES)/bsdiff
+			     $(HOST_OUT_EXECUTABLES)/imgdiff \
+	                     $(HOST_OUT_EXECUTABLES)/bsdiff
 	@echo "Construct recovery from boot"
 	mkdir -p $(dir $@)
 	$(HOST_OUT_EXECUTABLES)/imgdiff $(INSTALLED_BOOTIMAGE_TARGET) $(INSTALLED_RECOVERYIMAGE_TARGET) $@