fix writes to stdout and stderr

We want these in line buffered mode, but to get that we need to query the
console driver if it is a tty, and we can only do that after the VFS has
been brought up.

fs/vfs/main.c

@@ -1033,6 +1033,8 @@ void mount_rootfs(void)
 
 int console_init(void);
 
+int vfs_initialized;
+
 void
 vfs_init(void)
 {
@@ -1060,6 +1062,7 @@ vfs_init(void)
 		printf("failed to dup console (1)\n");
 	if (dup(0) != 2)
 		printf("failed to dup console (2)\n");
+	vfs_initialized = 1;
 }
 
 void sys_panic(const char *str)

libc/stdio/__stdout_write.c

@@ -2,9 +2,15 @@
 #include <termios.h>
 #include <sys/ioctl.h>
 
+extern int vfs_initialized;
+
 size_t __stdout_write(FILE *f, const unsigned char *buf, size_t len)
 {
 	struct termios tio;
+
+	if (!vfs_initialized)
+		return 0;
+		
 	f->write = __stdio_write;
 	if (!(f->flags & F_SVB) && ioctl(f->fd, TCGETS, &tio))
 		f->lbf = -1;