Add mknod utility to system/core/toolbox

Change-Id: I46586cba83ecb8095721be8ffad9e386d4698e4a
diff --git a/toolbox/Android.mk b/toolbox/Android.mk
index c5890b2..68b17ef 100644
--- a/toolbox/Android.mk
+++ b/toolbox/Android.mk
@@ -70,6 +70,7 @@
 	swapoff \
 	mkswap \
 	readlink \
+	mknod \
 	nohup
 
 ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))