code: function processAppSpecifiedDeclaration(allAppTypes, appType, decl) {
      let {prop, parent} = decl;
      let result;
      if ((result = SPECIFIED_APP_PROP_DECL_REGEXP.exec(prop))) {
          let propApp = result[1];
          let isMatchApp = appType === propApp;
          if (allAppTypes.includes(propApp) && !isMatchApp) {
              // remove not current app build type style declaration
              decl.remove();
          }
          else if (isMatchApp) {
              // remove the previous property style declaration that has same
              // style property name declaration that ignore app type prefix
              // and remove the specified app type prefix of the property
              let newPropName = prop.replace(SPECIFIED_APP_PROP_DECL_REGEXP, '');
              removeUnUseDecl(decl, newPropName);
              decl.prop = newPropName;
          }
  
          // remove empty rule
          if (!parent.nodes || !parent.nodes.length) {
              parent.remove();
          }
      }
  }
docs: Process specified app target css style property declaration
  
  @inner
  @param {Array.<string>} allAppTypes all supported build media target
  @param {string} appType the current build media target
  @param {Object} decl css style declaration