code: function flattenWrapFile(wrap, keyName, absFilePath) {
          var keyFileName = keyName + 'File';
  
          if (typeof wrap[keyName] !== 'string' && wrap[keyFileName]) {
              wrap[keyName] = '';
              if (typeof wrap[keyFileName] === 'string') {
                  wrap[keyFileName] = [wrap[keyFileName]];
              }
              wrap[keyFileName].forEach(function (fileName) {
                  wrap[keyName] += (wrap[keyName] ? '\n' : '') +
                      file.readFile(build.makeAbsPath(fileName, absFilePath));
              });
          } else if (typeof wrap[keyName] !== 'string') {
              throw new Error('wrap.' + keyName + ' or wrap.' + keyFileName + ' malformed');
          }
      }
docs: Converts a wrap.startFile or endFile to be start/end as a string.
  the startFile/endFile values can be arrays.