我想知道如何在 Mac 上正确设置环境变量。我的操作系统是 Mountain Lion，我在尝试运行“mvn clean install”时得到以下输出：
org.apache.maven.plugin.MojoExecutionException: No Android SDK path could be found. You may configure it in the plugin configuration section in the pom file using <sdk><path>...</path></sdk> or <properties><android.sdk.path>...</android.sdk.path></properties> or on command-line using -Dandroid.sdk.path=... or by setting environment variable ANDROID_HOME