Fix gradle incremental relast task.

build.gradle

@@ -69,14 +69,6 @@ task relast(type: JavaExec) {
     group = 'Build'
     main = "-jar"
 
-    doFirst {
-        delete "src/gen/jastadd/*.ast"
-        delete "src/gen/jastadd/RagConnect.jadd"
-        delete "src/gen/jastadd/RagConnectRefResolver.jadd"
-        delete "src/gen/jastadd/RagConnectResolverStubs.jrag"
-        mkdir  "src/gen/jastadd/"
-    }
-
     args = [
             "../libs/relast.jar",
             "../relast.preprocessor/src/main/jastadd/RelAst.relast",
@@ -90,14 +82,14 @@ task relast(type: JavaExec) {
             "--grammarName=./src/gen/jastadd/RagConnect"
     ]
 
-    inputs.files file("../libs/relast.jar"),
-            file("../relast.preprocessor/src/main/jastadd/RelAST.relast"),
-            file("./src/main/jastadd/RagConnect.relast")
-            file("./src/main/jastadd/MustacheNodes.relast")
-    outputs.files file("./src/gen/jastadd/RagConnect.ast"),
-            file("./src/gen/jastadd/RagConnect.jadd"),
-            file("./src/gen/jastadd/RagConnectRefResolver.jadd"),
-            file('./src/gen/jastadd/RagConnectResolverStubs.jrag')
+    inputs.files("../libs/relast.jar",
+            "../relast.preprocessor/src/main/jastadd/RelAST.relast",
+            "./src/main/jastadd/RagConnect.relast",
+            "./src/main/jastadd/MustacheNodes.relast")
+    outputs.files("./src/gen/jastadd/RagConnect.ast",
+            "./src/gen/jastadd/RagConnect.jadd",
+            "./src/gen/jastadd/RagConnectRefResolver.jadd",
+            './src/gen/jastadd/RagConnectResolverStubs.jrag')
 }
 
 jastadd {