Add instructions for installing the Android SDK

Author: abarth

getting-started.md

@@ -66,17 +66,10 @@ To learn more about how to build apps with Flutter, please see the
 Currently Flutter requires an Android device running
 Jelly Bean, v16, 4.1.x or later.
 
- - Install the `adb` tool from the [Android SDK](https://developer.android.com/sdk/installing/index.html?pkg=tools):
-   - Mac: `brew install android-platform-tools`
-   - Linux: `sudo apt-get install android-tools-adb`
-     - If the version of `adb` provided by your Linux distribution is too old,
-       you might need to [install the Android SDK manually](https://developer.android.com/sdk/installing/index.html?pkg=tools).
-       Note that `adb` needs 32-bit libs (on Ubuntu 64-bit, make sure to install
-       those libraries listed in _Troubleshooting Ubuntu_ section).
-         - Launch `Android SDK Manager` with `tools/android sdk`.
-         - Install `Android SDK Platform-tools` package that is the only required
-           package to use `adb`.
-         - Add `platform-tools/` to your `PATH`.
+ - Install the [Android SDK](https://developer.android.com/sdk/) and set the
+   `ANDROID_HOME` environment variable:
+  - Mac OS: `export ANDROID_HOME=$HOME/Library/Android/sdk`
+  - Linux: `export ANDROID_HOME=$HOME/Android/Sdk`
 
  - Enable developer mode on your device by visiting `Settings > About phone` and
    tapping the `Build number` field seven times.