fixed mooore derps in srg generation

Author: AbrarSyed

src/main/java/net/minecraftforge/gradle/tasks/dev/ObfuscateTask.java

@@ -61,10 +61,9 @@ public void doTask() throws IOException
 
         // copy srg
         File tempSrg = File.createTempFile("obf", ".srg", this.getTemporaryDir());
-        Files.copy(getSrg(), tempSrg);
 
         // append SRG
-        BufferedWriter writer = new BufferedWriter(new FileWriter(tempSrg, true));
+        BufferedWriter writer = Files.newWriter(tempSrg, Charset.defaultCharset());
         BufferedReader reader = Files.newReader(getSrg(), Charset.defaultCharset());
         for (String line1 : extraSrg)
         {