Make AutoFactory an isolating annotation processor in Gradle

RELNOTES=Gradle: `@AutoFactory` is now an isolating annotation processor

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=248771150

factory/pom.xml

@@ -82,6 +82,12 @@
       <version>1.0-rc4</version>
       <scope>provided</scope>
     </dependency>
+    <dependency>
+      <groupId>net.ltgt.gradle.incap</groupId>
+      <artifactId>incap</artifactId>
+      <version>0.2</version>
+      <scope>provided</scope>
+    </dependency>
     <dependency>
       <groupId>com.google.googlejavaformat</groupId>
       <artifactId>google-java-format</artifactId>

factory/src/main/java/com/google/auto/factory/processor/AutoFactoryProcessor.java

@@ -51,12 +51,15 @@
 import javax.lang.model.util.Elements;
 import javax.lang.model.util.Types;
 import javax.tools.Diagnostic.Kind;
+import net.ltgt.gradle.incap.IncrementalAnnotationProcessor;
+import net.ltgt.gradle.incap.IncrementalAnnotationProcessorType;
 
 /**
  * The annotation processor that generates factories for {@link AutoFactory} annotations.
  *
  * @author Gregory Kick
  */
+@IncrementalAnnotationProcessor(IncrementalAnnotationProcessorType.ISOLATING)
 @AutoService(Processor.class)
 public final class AutoFactoryProcessor extends AbstractProcessor {
   private FactoryDescriptorGenerator factoryDescriptorGenerator;