fix(core): asset bundling fails with BuildKit (#8911)

Docker buildkit has different output from the legacy builder unless you pass the -q flag in which case the output is always just the image tag. This PR works for both build versions.

----

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

packages/@aws-cdk/core/lib/bundling.ts

@@ -78,14 +78,14 @@ export class BundlingDockerImage {
     const buildArgs = options.buildArgs || {};
 
     const dockerArgs: string[] = [
-      'build',
+      'build', '-q',
       ...flatten(Object.entries(buildArgs).map(([k, v]) => ['--build-arg', `${k}=${v}`])),
       path,
     ];
 
     const docker = dockerExec(dockerArgs);
 
-    const match = docker.stdout.toString().match(/Successfully built ([a-z0-9]+)/);
+    const match = docker.stdout.toString().match(/sha256:([a-z0-9]+)/);
 
     if (!match) {
       throw new Error('Failed to extract image ID from Docker build output');

packages/@aws-cdk/core/test/test.bundling.ts

@@ -49,7 +49,7 @@ export = {
     const spawnSyncStub = sinon.stub(child_process, 'spawnSync').returns({
       status: 0,
       stderr: Buffer.from('stderr'),
-      stdout: Buffer.from(`Successfully built ${imageId}`),
+      stdout: Buffer.from(`sha256:${imageId}`),
       pid: 123,
       output: ['stdout', 'stderr'],
       signal: null,
@@ -63,7 +63,7 @@ export = {
     image._run();
 
     test.ok(spawnSyncStub.firstCall.calledWith('docker', [
-      'build',
+      'build', '-q',
       '--build-arg', 'TEST_ARG=cdk-test',
       'docker-path',
     ]));