概要

using UnityEditor;
using UnityEditor.Android;
using UnityEngine;

public static class Example
{
    [MenuItem( "Tools/Hoge" )]
    private static void Hoge()
    {
        Debug.Log( AndroidExternalToolsSettings.ndkRootPath );
        Debug.Log( AndroidExternalToolsSettings.sdkRootPath );
        Debug.Log( AndroidExternalToolsSettings.jdkRootPath );
        Debug.Log( AndroidExternalToolsSettings.gradlePath );
    }
}

上記のようなコードを記述することで

C:/Program Files/Unity/Hub/Editor/2019.3.2f1/Editor/Data/PlaybackEngines/AndroidPlayer/NDK
C:/Program Files/Unity/Hub/Editor/2019.3.2f1/Editor/Data/PlaybackEngines/AndroidPlayer\SDK
C:/Program Files/Unity/Hub/Editor/2019.3.2f1/Editor/Data/PlaybackEngines/AndroidPlayer\OpenJDK
C:/Program Files/Unity/Hub/Editor/2019.3.2f1/Editor/Data/PlaybackEngines/AndroidPlayer/Tools/gradle

このように Android SDK や Android NDK、JDK、Gradle のパスを取得できます