fix building from source

Author: mcr229

docs/source/using-executorch-building-from-source.md

@@ -63,7 +63,7 @@ Or alternatively, [install conda on your machine](https://conda.io/projects/cond
    ./install_executorch.sh
    ```
 
-   Use the [`--pybind` flag](https://github.com/pytorch/executorch/blob/main/install_executorch.sh#L26-L29) to install with pybindings and dependencies for other backends.
+   Use the [`--pybind` flag](https://github.com/pytorch/executorch/blob/release/0.6/install_executorch.sh#L26-L29) to install with pybindings and dependencies for other backends.
    ```bash
    ./install_executorch.sh --pybind <coreml | mps | xnnpack>
 
@@ -166,7 +166,7 @@ To further optimize the release build for size, use both:
 -DOPTIMIZE_SIZE=ON
 ```
 
-See [CMakeLists.txt](https://github.com/pytorch/executorch/blob/main/CMakeLists.txt)
+See [CMakeLists.txt](https://github.com/pytorch/executorch/blob/release/0.6/CMakeLists.txt)
 
 ### Build the runtime components
 
@@ -230,7 +230,7 @@ Assuming Android NDK is available, run:
 mkdir cmake-android-out && cd cmake-android-out
 
 # point -DCMAKE_TOOLCHAIN_FILE to the location where ndk is installed
-cmake -DCMAKE_TOOLCHAIN_FILE=/Users/{user_name}/Library/Android/sdk/ndk/27.2.12479018/build/cmake/android.toolchain.cmake  -DANDROID_ABI=arm64-v8a ..
+cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake  -DANDROID_ABI=arm64-v8a ..
 
 cd  ..
 cmake --build  cmake-android-out  -j9