code: function(inputPath, outputPath, outputCharset){
          var target = path.resolve(inputPath),
              result = {
                  'success': true,
                  'files': []
              };
          if(fs.existsSync(target)){
              if(fs.statSync(target).isDirectory()) {
                  var targets = fs.readdirSync(target);
                  for (var i in targets) {
                      if(!ModuleCompiler.isFileIgnored(targets[i])){
                          var inputFile = path.resolve(target, targets[i]),
                              outputFile = path.join(outputPath, targets[i]);
                          if(path.extname(inputFile)==='.js') {
                              result.files.push(ModuleCompiler.build(inputFile, outputFile, outputCharset));
                          }
                      }
                  }
              } else {
                  result.files.push(ModuleCompiler.build(target, outputPath, outputCharset));
              }
          }else{
              // MC.build('pkgName/abc');
              var modulePath = ModuleCompiler.getModulePath(inputPath);
              if(modulePath){
                  result.files.push(ModuleCompiler.build(modulePath, outputPath, outputCharset));
              }else{
                  result.success = false;
                  !ModuleCompiler._config.silent && console.info('[err]'.bold.red + ' cannot find target: %s', target);
              }
          }
          return result;
      }
docs: build a file or a directory
  @param inputPath {String} the source file location.
  @param outputPath {String} the combined file location.
  @param outputCharset {String} the combined file charset. default to 'utf-8'
  @return {Object}