第一次adb remount提示成功，但实际上system还是无法写入。再次adb remount即报错：
C:\Windows\SysWOW64>adb remount
remount of /system failed: Read-only file system
remount failed

解决：
diff --git a/device/rockchip/rk3399/rk3399_all.mk b/device/rockchip/rk3399/rk3399_all.mk
index 7a2d870..24c8d16 100755
--- a/device/rockchip/rk3399/rk3399_all.mk
+++ b/device/rockchip/rk3399/rk3399_all.mk
@@ -38,7 +38,8 @@ BUILD_WITH_GOOGLE_MARKET_ALL := false
 BUILD_WITH_GOOGLE_FRP := false
 
 #for data encrypt options
-BUILD_WITH_FORCEENCRYPT := true
+#BUILD_WITH_FORCEENCRYPT := true
+BUILD_WITH_FORCEENCRYPT := false