KAFKA-4082; Upgrade to Gradle 3.0

Also upgrade scoverage (required for compatibility) and remove usage of
`useAnt` which doesn't exist in Gradle 3.0

It turns out that one cannot even run `gradle` to download the project Gradle version if `useAnt` is used in the build. This is unfortunate (the SBT launcher has much saner behaviour).

Release notes: https://docs.gradle.org/3.0/release-notes

Author: Ismael Juma <ismael@juma.me.uk>

Reviewers: Grant Henke <granthenke@gmail.com>, Ewen Cheslack-Postava <ewen@confluent.io>, Sriharsha Chintalapani <harsha@hortonworks.com>

Closes #1774 from ijuma/kafka-4082-support-gradle-3.0

build.gradle

@@ -26,7 +26,7 @@ buildscript {
     // For Apache Rat plugin to ignore non-Git files
     classpath "org.ajoberstar:grgit:1.5.0"
     classpath 'com.github.ben-manes:gradle-versions-plugin:0.12.0'
-    classpath 'org.scoverage:gradle-scoverage:2.0.1'
+    classpath 'org.scoverage:gradle-scoverage:2.1.0'
   }
 }
 
@@ -68,7 +68,7 @@ allprojects {
 }
 
 ext {
-  gradleVersion = "2.14.1"
+  gradleVersion = "3.0"
   buildVersionFileName = "kafka-version.properties"
 
   userMaxForks = project.hasProperty('maxParallelForks') ? maxParallelForks.toInteger() : null
@@ -236,8 +236,6 @@ subprojects {
   }
 
   tasks.withType(ScalaCompile) {
-    scalaCompileOptions.useAnt = false
-
     scalaCompileOptions.additionalParameters = [
       "-deprecation",
       "-unchecked",

gradlew

@@ -161,4 +161,9 @@ function splitJvmOpts() {
 eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS
 JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME"
 
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [[ "$(uname)" == "Darwin" ]] && [[ "$HOME" == "$PWD" ]]; then
+  cd "$(dirname "$0")"
+fi
+
 exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"

gradlew.bat

@@ -49,7 +49,6 @@ goto fail
 @rem Get command-line arguments, handling Windows variants
 
 if not "%OS%" == "Windows_NT" goto win9xME_args
-if "%@eval[2+2]" == "4" goto 4NT_args
 
 :win9xME_args
 @rem Slurp the command line arguments.
@@ -60,11 +59,6 @@ set _SKIP=2
 if "x%~1" == "x" goto execute
 
 set CMD_LINE_ARGS=%*
-goto execute
-
-:4NT_args
-@rem Get arguments from the 4NT Shell from JP Software
-set CMD_LINE_ARGS=%$
 
 :execute
 @rem Setup the command line