fix(ecs): respect LogGroup's region for aws-log-driver (aws#18212)

Respect passed log group `region` when constructing an instance of `AwsLogDriver`.
That change allows to implement cross region logging pattern for ECS containers.

fixes aws#17747

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-ecs/lib/log-drivers/aws-log-driver.ts

@@ -1,5 +1,4 @@
 import * as logs from '@aws-cdk/aws-logs';
-import { Stack } from '@aws-cdk/core';
 import { ContainerDefinition } from '../container-definition';
 import { LogDriver, LogDriverConfig } from './log-driver';
 import { removeEmpty } from './utils';
@@ -127,7 +126,7 @@ export class AwsLogDriver extends LogDriver {
       options: removeEmpty({
         'awslogs-group': this.logGroup.logGroupName,
         'awslogs-stream-prefix': this.props.streamPrefix,
-        'awslogs-region': Stack.of(containerDefinition).region,
+        'awslogs-region': this.logGroup.env.region,
         'awslogs-datetime-format': this.props.datetimeFormat,
         'awslogs-multiline-pattern': this.props.multilinePattern,
         'mode': this.props.mode,

packages/@aws-cdk/aws-ecs/test/aws-log-driver.test.ts

@@ -155,4 +155,38 @@ describe('aws log driver', () => {
 
 
   });
+
+  test('allows cross-region log group', () => {
+    // GIVEN
+    const logGroupRegion = 'asghard';
+    const logGroup = logs.LogGroup.fromLogGroupArn(stack, 'LogGroup',
+      `arn:aws:logs:${logGroupRegion}:1234:log-group:my_log_group`);
+
+    // WHEN
+    td.addContainer('Container', {
+      image,
+      logging: new ecs.AwsLogDriver({
+        logGroup,
+        streamPrefix: 'hello',
+      }),
+    });
+
+    // THEN
+    expect(stack).toCountResources('AWS::Logs::LogGroup', 0);
+    expect(stack).toHaveResourceLike('AWS::ECS::TaskDefinition', {
+      ContainerDefinitions: [
+        {
+          LogConfiguration: {
+            LogDriver: 'awslogs',
+            Options: {
+              'awslogs-group': logGroup.logGroupName,
+              'awslogs-stream-prefix': 'hello',
+              'awslogs-region': logGroupRegion,
+            },
+          },
+        },
+      ],
+    });
+  });
+
 });