tools/Config.mk: suppress all normal output for cmp

Fix build break:
make: *** No rule to make target 'byte', needed by 'differ'.  Stop.

Regression by:
-----------------------------------------------------
|commit 0951f70df6
|
|    Improve dependencies for include/nuttx/version.h
-----------------------------------------------------

Signed-off-by: chao.an <anchao@xiaomi.com>

tools/Config.mk

@@ -508,7 +508,7 @@ endef
 else
 define TESTANDREPLACEFILE
 	if [ -f $2 ]; then \
-		if cmp $1 $2; then \
+		if cmp -s $1 $2; then \
 			rm -f $1; \
 		else \
 			mv $1 $2; \