Makefile: Fix gtags generation

We should use "-print" or otherwise all "-prone" is ignored.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210804132328.41353-2-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/Makefile b/Makefile
index fe9415a..1b36bf2 100644
--- a/Makefile
+++ b/Makefile
@@ -256,7 +256,7 @@
 		"GTAGS", "Remove old $@ files")
 	$(call quiet-command, 				\
 	        (cd $(SRC_PATH) && 			\
-		 $(find-src-path) | gtags -f -), 	\
+		 $(find-src-path) -print | gtags -f -),	\
 		"GTAGS", "Re-index $(SRC_PATH)")
 
 .PHONY: TAGS