Move publicized assembly cache to system temp directory

People kept publishing their Source/obj directories (containing the entire Celeste code),
so let's see how this will go

CelesteMod.Publicizer/CelestePublicizerTask.cs

@@ -47,8 +47,16 @@ public override bool Execute() {
             return false;
         }
 
-        string outputAssemblyPath = $"{IntermediateOutputPath}Celeste-publicized.dll";
-        string outputHashPath = $"{outputAssemblyPath}.md5";
+        // Clear old leftover DLLs
+        if (File.Exists($"{IntermediateOutputPath}Celeste-publicized.dll"))
+            File.Delete($"{IntermediateOutputPath}Celeste-publicized.dll");
+        if (File.Exists($"{IntermediateOutputPath}Celeste-publicized.dll.md5"))
+            File.Delete($"{IntermediateOutputPath}Celeste-publicized.dll.md5");
+        if (File.Exists($"{IntermediateOutputPath}Celeste-publicized.xml"))
+            File.Delete($"{IntermediateOutputPath}Celeste-publicized.xml");
+
+        string outputAssemblyPath = Path.Combine(Path.GetTempPath(), "Celeste-publicized.dll");
+        string outputHashPath = Path.ChangeExtension(outputAssemblyPath, "md5");
 
         var taskAssembly = typeof(PublicizeCelesteTask).Assembly;