build-toolsを自動で設定する

build.gradle

apply plugin: 'com.android.application'

def getSdkDir() {
    Properties properties = new Properties()
    properties.load(project.rootProject.file('local.properties').newDataInputStream())
    def sdkDir = properties.getProperty('sdk.dir', null)
    if (sdkDir == null)
        throw new GradleException("SDK location not found. Define location with sdk.dir in the local.properties file or with an ANDROID_SDK_ROOT environment variable.")

    return sdkDir
}

def buildToolsList(){
    new File(getSdkDir(), 'build-tools').list().sort { a, b -> b <=> a }
}

def latestBuildTools(){
    buildToolsList()[0]
}

android {
    compileSdkVersion 22
    buildToolsVersion latestBuildTools()

    defaultConfig {
        applicationId "com.litmon.build-tools-automation"
        minSdkVersion 15
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.0'
}