fix(assets): run executable command of container assets in cloud asse…

…mbly root directory (#16094)

Runs the executable command of container assets in the cloud assembly root directory and not the current directory.

Could be a breaking change.

fixes #15721
----

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

packages/cdk-assets/lib/private/handlers/container-images.ts

@@ -83,14 +83,16 @@ export class ContainerImageAssetHandler implements IAssetHandler {
    * External command is responsible for deduplicating the build if possible,
    * and is expected to return the generated image identifier on stdout.
    */
-  private async buildExternalAsset(executable: string[]): Promise<string | undefined> {
+  private async buildExternalAsset(executable: string[], cwd?: string): Promise<string | undefined> {
+
+    const assetPath = cwd ?? this.workDir;
+
     this.host.emitMessage(EventType.BUILD, `Building Docker image using command '${executable}'`);
     if (this.host.aborted) { return undefined; }
 
-    return (await shell(executable, { quiet: true })).trim();
+    return (await shell(executable, { cwd: assetPath, quiet: true })).trim();
   }
 
-
   /**
    * Check whether the image already exists in the ECR repo
    *

packages/cdk-assets/test/docker-images.test.ts

@@ -183,7 +183,7 @@ describe('external assets', () => {
 
     const expectAllSpawns = mockSpawn(
       { commandLine: ['docker', 'login', '--username', 'user', '--password-stdin', 'https://proxy.com/'] },
-      { commandLine: ['sometool'], stdout: externalTag },
+      { commandLine: ['sometool'], stdout: externalTag, cwd: '/external/cdk.out' },
       { commandLine: ['docker', 'tag', externalTag, '12345.amazonaws.com/repo:ghijkl'] },
       { commandLine: ['docker', 'push', '12345.amazonaws.com/repo:ghijkl'] },
     );