Angular 8 支持多域名多站点的解决方法如下：

1. 在Angular项目的根目录中创建一个新的配置文件，命名为multi-site.config.json，并在该文件中定义多个域名和对应的站点配置。示例：

{
  "sites": [
    {
      "domain": "site1.com",
      "siteName": "Site 1",
      "baseHref": "/"
    },
    {
      "domain": "site2.com",
      "siteName": "Site 2",
      "baseHref": "/site2/"
    }
  ]
}

2. 在angular.json文件中添加一个新的项目配置，用于处理多域名和多站点的构建。示例：

{
  "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
  "version": 1,
  "newProjectRoot": "projects",
  "projects": {
    "multi-site": {
      "projectType": "application",
      "schematics": {},
      "architect": {
        "build": {
          "builder": "@angular-devkit/build-angular:browser",
          "options": {
            "outputPath": "dist/multi-site",
            "index": "src/index.html",
            "main": "src/main.ts",
            "polyfills": "src/polyfills.ts",
            "tsConfig": "src/tsconfig.app.json",
            "assets": [
              "src/favicon.ico",
              "src/assets"
            ],
            "styles": [
              "src/styles.scss"
            ],
            "scripts": []
          },
          "configurations": {
            "site1": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.site1.ts"
                }
              ]
            },
            "site2": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.site2.ts"
                }
              ]
            }
          }
        },
        "serve": {
          "builder": "@angular-devkit/build-angular:dev-server",
          "options": {
            "browserTarget": "multi-site:build"
          },
          "configurations": {
            "site1": {
              "browserTarget": "multi-site:build:site1"
            },
            "site2": {
              "browserTarget": "multi-site:build:site2"
            }
          }
        }
      }
    }
  },
  "defaultProject": "multi-site"
}

3. 在src目录下创建多个环境配置文件，每个站点一个。例如，分别创建environment.site1.ts和environment.site2.ts，并在这些文件中定义对应站点的配置。示例：

export const environment = {
  production: true,
  apiUrl: 'https://api.site1.com'
};

4. 在src目录下创建一个多站点的入口文件，例如main-multi-site.ts，并在该文件中根据当前域名动态选择对应的站点配置。示例：

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { environment } from './environments/environment';
import { environment as site1Environment } from './environments/environment.site1';
import { environment as site2Environment } from './environments/environment.site2';
import { AppModule } from './app/app.module';

// 根据当前域名动态选择站点配置
let selectedEnvironment = environment;
if (window.location.hostname === 'site1.com') {
  selectedEnvironment = site1Environment;
} else if (window.location.hostname === 'site2.com') {
  selectedEnvironment = site2Environment;
}

if (selectedEnvironment.production) {
  enableProdMode();
}

platformBrowserDynamic([{ provide: 'APP_CONFIG', useValue: selectedEnvironment }])
  .bootstrapModule(AppModule)
  .catch(err => console.error(err));

5. 修改angular.json文件中的main属性，将其指向多站点的入口文件main-multi-site.ts。示例：

{
  "projects": {
    "multi-site": {
      "architect": {
        "build": {
          "options": {
            "main": "src/main-multi-site.ts"
          }
        },
        "serve": {
          "options": {
            "browserTarget": "multi-site:build"