Thanks @xiaolu 
@xiaolu URL:
https://github.com/xiaolu

需要修改build/core/qcom_utils.mk 加一句：
QCOM_BOARD_PLATFORMS += msm8939

android_device_htc_htc_a51dtul
HTC D820 Recovery Device

Clone:
git clone https://github.com/Mr-zeng/android_device_htc_htc_a51dtul.git -b cm-11.0


Only Make Recoveryimage
仅限编译Recovery

If you need to reprint, please as far as possible with my name, thank you!
如果你需要转载的话，请尽可能的说明出处，谢谢！