runAsync method
Run pub run on the given package and script.
If script is null it defaults to the same value as package.
Implementation
static Future<String> runAsync(String package,
{List<String> arguments, RunOptions runOptions, String script}) {
var scriptArg = script == null ? package : '$package:$script';
List<String> args = ['run', scriptArg];
if (arguments != null) args.addAll(arguments);
return runlib.runAsync(sdkBin('pub'),
arguments: args, runOptions: runOptions);
}