makefile: fix assembler detection on solaris

Assembler test waited forever for input (missing /dev/null input
redirection for as -V).
(cherry picked from commit 0f7ec046ce88202e508ced7c1b1d544f05529758)

Makefile.defs

@@ -683,7 +683,8 @@ ifeq ($(CC_NAME), gcc)
 						fi)
 		ASPATH:=$(shell  if [ -z "$(ASGCC)" ] ; then echo "as" ;\
 						else \
-						if $(ASGCC) -V 2>/dev/null 1>/dev/null; then \
+						if $(ASGCC) -V 2>/dev/null 1>/dev/null </dev/null; \
+						then \
 							echo $(ASGCC); \
 						else echo "as" ; \
 						fi\