Using the local.properties file of an Android Studio project to select the latest BuildTools version

build.gradle

apply plugin: 'com.android.library'

android {
    compileSdkVersion 'Google Inc.:Google APIs:22'

    Properties localProps = new Properties()
    localProps.load(new FileInputStream(file('../local.properties')))
    def buildToolVer = file("${localProps['sdk.dir']}/build-tools/").listFiles().sort().reverse().first().name;
    buildToolsVersion buildToolVer;

    defaultConfig {
        minSdkVersion 16
        targetSdkVersion 22
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
    publishNonDefault true
}