Update to gradle 4.7, fix nullability issue in buildSrc

JavaExec args list is nullable now, so use orEmpty before copying it.

buildSrc/src/main/kotlin/SmartJavaExec.kt

@@ -39,7 +39,7 @@ fun Project.smartJavaExec(configure: JavaExec.() -> Unit) = task<JavaExec> javaE
         main = "-jar"
 
         classpath = project.files()
-        val copyArgs = mutableListOf<Any?>().also { it.addAll(args) }
+        val copyArgs = args.orEmpty().toList()
         args(jarTask.outputs.files.singleFile)
         args(copyArgs)
 

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.7-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists