TIL: to get Gradle to use external Maven dependencies, you need to declare repositories OUTSIDE 'buildscript'. If you don't, you get an error telling you Gradle can't resolve whatever external dependencies your project depend on.

build.gradle

buildscript {

    repositories {
        maven {
            url 'http://repo1.maven.org/maven2'
        }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.4'
    }
}

repositories {
    maven {
        url 'http://google-api-client-libraries.appspot.com/mavenrepo'
    }

    maven {
        url 'http://repo1.maven.org/maven2'
    }
}

apply plugin: 'android'


dependencies {
    // compile files('libs/android-support-v4.jar')
    compile 'com.android.support:support-v4:13.0.0'
    compile 'com.google.android.gms:play-services:3.1.36'
    compile 'com.google.http-client:google-http-client-jackson2:1.13.1-beta'
    compile 'com.google.apis:google-api-services-youtube:v3-rev24-1.13.2-beta'
    compile 'com.google.oauth-client:google-oauth-client-jetty:1.13.1-beta'
}

android {
    compileSdkVersion 17
    buildToolsVersion "17"

    defaultConfig {
        minSdkVersion 8
        targetSdkVersion 16
    }
}