fix separator on linux for forge

VeloeMinecraftLauncher/MinecraftLauncher/StartCommandBuilder.cs

@@ -177,7 +177,7 @@ internal static class StartCommandBuilder
                     }
                     if (value.Contains("${classpath_separator}"))
                     {
-                        value = value.Replace("${classpath_separator}", ";");
+                        value = value.Replace("${classpath_separator}", separator.ToString());
                     }
 
                     returnString.Append(" ");