Update BUILD.md with Android NDK instructions

Added instructions for downloading Android NDK and building QAI AppBuilder.

Signed-off-by: shengtin <shengtin@qti.qualcomm.com>

Author: tim202503

BUILD.md

@@ -60,6 +60,7 @@ Run below command in Windows terminal:
 ```
 git clone https://github.com/quic/ai-engine-direct-helper.git --recursive
 ```
+
 ### Set PATH and run make.exe to build QAI AppBuilder
 • Download [android ndk](https://dl.google.com/android/repository/android-ndk-r26d-windows.zip).<br>
 • Run following commands in Windows terminal:
@@ -116,4 +117,4 @@ chmod +x ./superresolution
 
 • Root cause<br>
 Above error info is due to version incompatible between libappbuilder.so and QAIRT sdk version. 
-It is resolved by recompile libappbuilder.so after set correct QNN_SDK_ROOT.
+It is resolved by recompile libappbuilder.so after set correct QNN_SDK_ROOT.