Use the Lambda arch from the deployment machine

There seems to be some kind of bug that the 'platform' parameter to the
code bundling is ignored. When specifying ARM64 as the architecture for
my lamda, and platform, the lambda bundling (docker buildx) just uses
the host architecture.

src/constants.ts

@@ -2,5 +2,5 @@ import { Architecture, Runtime } from 'aws-cdk-lib/aws-lambda';
 
 export class Constants {
   static readonly LAMBDA_RUNTIME = Runtime.PYTHON_3_12;
-  static readonly LAMBDA_ARCH = Architecture.ARM_64;
+  static readonly LAMBDA_ARCH = process.arch === 'arm64' ? Architecture.ARM_64 : Architecture.X86_64;
 }