anchor.diff:    --compile-sdk=<patched_sdk>
       Compile the SDK from scratch instead of reading it from 'platform.dill'.
   
  +  --sdk=<patched_sdk>
  +    Location of the SDK sources for use when compiling additional platform
  +    libraries.
  +
     --fatal=errors
     --fatal=warnings
     --fatal=nits
  
positive.code:     }
      if (options.containsKey("-t") && options.containsKey("--target")) {
        return argumentError(usage, "Can't specify both '-t' and '--target'.");
      }
      if (programName == "compile_platform" && arguments.length != 3) {
        return argumentError(usage, "Expected three arguments.");
  
negative.code: 
    Uri get packages => options["--packages"] ?? Uri.base.resolve(".packages");
  
    Uri get sdk => options["--sdk"] ?? options["--compile-sdk"];
  
    Set<String> get fatal {
      return new Set<String>.from(options["--fatal"] ?? <String>[]);
  