Exclude Duplicates (#860)

addon.gradle

@@ -2,7 +2,6 @@ compileJava {
     options.encoding = "UTF-8"
 }
 
-
 generateGrammarSource {
     maxHeapSize = "128m"
     arguments += ['-package', 'codechicken.nei.search', '-visitor', '-no-listener']
@@ -12,6 +11,10 @@ generateGrammarSource {
 compileJava.dependsOn generateGrammarSource
 sourcesJar.dependsOn generateGrammarSource
 
+sourcesJar {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+}
+
 sourceSets {
     main {
         java.srcDirs += ["build/generated/sources/search/antlr/"]