Use Animal Sniffer to check Java 6 API compatibility.

build.gradle

@@ -22,30 +22,7 @@ buildscript {
 		classpath 'com.android.tools.build:gradle:3.1.2'
 		classpath 'net.ltgt.gradle:gradle-apt-plugin:0.9'
 		classpath 'de.undercouch:gradle-download-task:3.2.0'
+		classpath 'ru.vyarus:gradle-animalsniffer-plugin:1.4.3'
 		classpath files('libs/gradle-witness.jar')
 	}
 }
-
-// If a Java 6 JRE is available, check we're not using any Java 7 or 8 APIs
-ext.useJava6StandardLibrary = { task ->
-	def home = System.env.JAVA_6_HOME;
-	if (home != null && !home.isEmpty()) {
-		println "Setting Java 6 bootstrap classpath for ${task.name}"
-		task.dependsOn createJavaLangInvokeJar
-		task.options.bootstrapClasspath = files(
-				"${project.rootDir}/build/invoke.jar",
-				"${home}/jre/lib/rt.jar",
-				"${home}/jre/lib/jsse.jar"
-		)
-	}
-}
-
-// Create a jar containing the java.lang.invoke classes for the Java 6 bootstrap classpath
-task createJavaLangInvokeJar(type: Zip) {
-	archiveName 'invoke.jar'
-	destinationDir file("${project.rootDir}/build")
-	from zipTree("${System.getProperty('java.home')}/lib/rt.jar").matching {
-		include 'java/lang/invoke/*'
-	}
-	include '**/*'
-}