AWS Fargate无法根据环境变量来运行构建。为了解决这个问题，您可以使用AWS CodePipeline和AWS CodeBuild来自动化构建和部署过程。在pipeline中，您可以定义不同的stage和环境变量，以使构建在不同的环境中运行。以下是一个使用AWS CodePipeline和AWS CodeBuild的简单示例：

1. 创建一个CodeBuild项目

aws codebuild create-project --name my-project --source "type=GITHUB,integration=jenkins" --environment "type=LINUX_CONTAINER,image=aws/codebuild/standard:2.0" --artifacts "type=NO_ARTIFACTS"

2. 在CodePipeline中定义不同的stage和环境变量

{
  "stages": [
    {
      "name": "Build",
      "actions": [
        {
          "name": "Build",
          "actionTypeId": {
            "category": "Build",
            "owner": "AWS",
            "provider": "CodeBuild",
            "version": "1"
          },
          "configuration": {
            "ProjectName": "my-project"
          },
          "outputArtifacts": [
            {
              "name": "BuiltArtifact"
            }
          ],
          "inputArtifacts": []
        }
      ]
    },
    {
      "name": "Deploy",
      "actions": [
        {
          "name": "Deploy-Test",
          "actionTypeId": {
            "category": "Deploy",
            "owner": "AWS",
            "provider": "ECS",
            "version": "1"
          },
          "configuration": {
            "ClusterName": "my-cluster-test",
            "ServiceName": "my-service-test",
            "ImageURI": "#{SourceVariables.DOCKER_IMAGE_URI}"
          },
          "inputArtifacts": [
            {
              "name": "BuiltArtifact"
            }
          ]
        },
        {
          "name": "Deploy-Prod",
          "actionTypeId": {
            "category": "Deploy",
            "owner": "AWS",
            "provider": "ECS",
            "version": "1"
          },
          "configuration": {
            "ClusterName": "my-cluster-prod",
            "ServiceName": "my-service-prod",
            "ImageURI": "#{SourceVariables.DOCKER_IMAGE_URI}"
          },
          "inputArtifacts": [
            {
              "name": "BuiltArtifact"
            }
          ]
        }
      ]
    }
  ],
  "artifactStores": {
    "S3": {
      "type": "S3",
      "location": "my-bucket"
    }
  }
}

此示例定义了两个stage：Build和Deploy。在Deploy stage中，有两个具有不同环境变量的部署操作（test和prod）。在pipeline运行期间，您可以定义环境变量来指定要运行哪个操作。

注意，此示例仅用于说明目的，具体实现方法可能因环境而异。