Update to ndk 18
diff --git a/HOW-TO-BUILD.md b/HOW-TO-BUILD.md
index 58fd017..565a3f1 100644
--- a/HOW-TO-BUILD.md
+++ b/HOW-TO-BUILD.md
@@ -32,7 +32,7 @@
This script will build Android and iOS SDKs:
> `$ bash scripts/build_from_source.sh $NDK18_dir`
-The `$NDK18_dir` and `$NDK16_dir` should be the directory of NDK 18, otherwise the Android build would failed.
+The `$NDK18_dir` should be the directory of NDK 18, otherwise the Android build would failed.
This may take a while. After that, you can look in `dist/`, `android/sdk/build/output/` and `ios/sdk/Products` for Web/Android/iOS SDK artifacts.
@@ -61,11 +61,11 @@
check env
- you have gradle installed, see more details about 'how to install gradle' on the [gradle website](https://gradle.org/install).
-- NDK r16 [link](https://developer.android.com/ndk/)
+- [NDK r18](https://developer.android.com/ndk/downloads/older_releases.html)
- edit local.propteries (in `Android` dir)
```
- ndk.dir=/Users/{user}/Library/Android/sdk/ndk-bundle-r16
+ ndk.dir=/Users/{user}/Library/Android/sdk/ndk-bundle-r18
sdk.dir=/Users/{user}/Library/Android/sdk
```
