Remove need to manually set wrapper GRADLE_OPTS

Replace the wrapper task with a variant that automatically adds the
appropriate GRADLE_OPTS to the shell and bat files.

Author: philwebb

build.gradle

@@ -805,3 +805,12 @@ configure(rootProject) {
     }
 }
 
+def defaultWrapper = tasks["wrapper"]
+task wrapper(overwrite: true, dependsOn: defaultWrapper) << {
+    def gradleOpts = "-XX:MaxPermSize=1024m -Xmx1024m -XX:MaxHeapSize=256m"
+    File wrapperFile = file('gradlew')
+    wrapperFile.text = wrapperFile.text.replace("DEFAULT_JVM_OPTS=", "GRADLE_OPTS=\"$gradleOpts \$GRADLE_OPTS\"\nDEFAULT_JVM_OPTS=")
+    File wrapperBatFile = file('gradlew.bat')
+    wrapperBatFile.text = wrapperBatFile.text.replace("set DEFAULT_JVM_OPTS=", "set GRADLE_OPTS=$gradleOpts %GRADLE_OPTS%\nset DEFAULT_JVM_OPTS=")
+}
+