Add auto-generated files

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/library/Makefile b/library/Makefile
index eb3b901..c1ec9c6 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -345,7 +345,7 @@
 generated_files: $(GENERATED_FILES)
 
 # See root Makefile
-GEN_FILES ?= yes
+GEN_FILES ?=
 ifdef GEN_FILES
 gen_file_dep =
 else