Fix a build error

build.gradle

@@ -87,8 +87,10 @@ task buildResources {
     doLast {
         File to = new File("${buildDir}/classes/java/main/META-INF/services/javax.annotation.processing.Processor")
         to.parentFile.mkdirs()
-        to.createNewFile()
-        to.append("de.steamwar.linkage.LinkageProcessor\n")
+        if (!to.exists()) {
+            to.createNewFile()
+            to.append("de.steamwar.linkage.LinkageProcessor\n")
+        }
     }
 }
 classes.finalizedBy(buildResources)