Fix mkinitrd, add vfs_initrd stub
diff --git a/src/kernel/kint.h b/src/kernel/kint.h
index 8f934fa..d892f88 100644
--- a/src/kernel/kint.h
+++ b/src/kernel/kint.h
@@ -16,3 +16,5 @@
 };
 
 #define NULL 0
+#define MIN(a, b) ((a)>(b)?(b):(a))
+#define MAX(a, b) ((a)>(b)?(a):(b))