sam sync throws "Build method missing" error on static nodejs modules

I am using nodejs and "sam sync". I have a layer with shared js code that doesn't need to be built. I am using ES Modules for imports.

While I have this working, any changes to my shared code module results in a "Build method missing in layer" error making quick iteration difficult.

SAM CLI, version 1.70.0

Directory structure:

layers-test/{template.yaml, samconfig.toml}
layers-test/hello-world/{app.js, package.json}
layers-test/shared-code/tools/{tools.js, package.json}
layers-test/shared-code/util/{util.js, package.json}
layers-test/shared-modules/{package.json, package-lock.json, node_modules/}

hello-world/app.js:

import pick from "lodash.pick";
import { utilFunction } from "/opt/util/util.js";
import { toolsFunction } from "/opt/tools/tools.js";

export const lambdaHandler = async (event, context) => {
    try {
        utilFunction();
        toolsFunction();
        console.log('rez:', pick({ a: 40, b: 30, c: 20 }, ['a', 'b']));
        return {
            'statusCode': 200,
            'body': JSON.stringify({
                message: 'hello world',
            })
        }
    } catch (err) {
        console.log(err);
        return err;
    }
};

shared-modules/package.json:

{
  "name": "shared-modules",
  "version": "1.0.0",
  "description": "",
  "dependencies": {
    "lodash.pick": "^4.4.0"
  }
}

shared-code/util/util.js:

export const utilFunction = () => {
  console.log('running utilFunction');
};

shared-code/util/package.json:

{
  "name": "util",
  "version": "1.0.0",
  "description": "",
  "main": "util.js",
  "type": "module"
}

template.yaml:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  layers-test

  Sample SAM Template for layers-test

Globals:
  Function:
    Timeout: 3

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs18.x
      Architectures:
        - x86_64
      Layers:
        - !Ref SharedModulesLayer
        - !Ref SharedCodeLayer
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get

  SharedModulesLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      ContentUri: layers/shared-modules
      CompatibleRuntimes:
        - nodejs18.x
    Metadata:
      BuildMethod: nodejs18.x
      BuildArchitecture: x86_64
  SharedCodeLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      ContentUri: layers/shared-code
      CompatibleRuntimes:
        - nodejs18.x

All of this code works, but with sam sync active, whenever I make changes to anything in shared-code/ I get the error:

Syncing Layer SharedCodeLayer...
Layer <samcli.lib.providers.sam_function_provider.SamFunctionProvider object at 0x7f19797b81d0> is missing BuildMethod Metadata.
Code sync encountered an error.
Traceback (most recent call last):
  File "samcli/lib/sync/sync_flow_executor.py", line 342, in _sync_flow_execute_wrapper
  File "samcli/lib/sync/sync_flow.py", line 310, in execute
  File "samcli/lib/sync/flows/layer_sync_flow.py", line 224, in gather_resources
  File "samcli/commands/build/build_context.py", line 523, in collect_build_resources
  File "samcli/commands/build/build_context.py", line 611, in _collect_single_buildable_layer
samcli.commands.build.exceptions.MissingBuildMethodException: Build method missing in layer SharedCodeLayer.

If I add:

    Metadata:
      BuildMethod: nodejs18.x
      BuildArchitecture: x86_64

to SharedCodeLayer then the imports no longer work. I get an error like:

Uncaught Exception      {"errorType":"Error","errorMessage":"Cannot find module '/opt/util/util.js' imported from /var/task/app.js","code":"ERR_MODULE_NOT_FOUND","stack":["Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/opt/util/util.js' imported from /var/task/app.js","    at new NodeError (node:internal/errors:393:5)","    at finalizeResolution (node:internal/modules/esm/resolve:328:11)","    at moduleResolve (node:internal/modules/esm/resolve:965:10)","    at moduleResolveWithNodePath (node:internal/modules/esm/resolve:909:12)","    at defaultResolve (node:internal/modules/esm/resolve:1173:79)","    at nextResolve (node:internal/modules/esm/loader:163:28)","    at ESMLoader.resolve (node:internal/modules/esm/loader:841:30)","    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:424:18)","    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:76:40)","    at link (node:internal/modules/esm/module_job:75:36)"]}

Is there any way to make these imports work while avoiding the "Build method missing in layer" in error?