Only check header for non-generated files

For generated files, it is enough to check the headers of the
files they are generated from. Moreover, the generated files
have the shebang-line of the target system, which might be
different from the generic one checked for.
Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Niklas Hambuechen <niklash@google.com>

Makefile.am

@@ -2048,7 +2048,8 @@ check-news:
 .PHONY: check-local
 check-local: check-dirs check-news $(GENERATED_FILES)
 	$(CHECK_PYTHON_CODE) $(check_python_code)
-	PYTHONPATH=. $(CHECK_HEADER) $(check_python_code)
+	PYTHONPATH=. $(CHECK_HEADER) \
+	    $(filter-out $(GENERATED_FILES),$(check_python_code))
 	$(CHECK_VERSION) $(VERSION) $(top_srcdir)/NEWS
 	PYTHONPATH=. $(RUN_IN_TEMPDIR) $(CURDIR)/$(CHECK_IMPORTS) . $(standalone_python_modules)
 	error= ; \