This PR improves the error message when a lambda-nodejs function fails to bundle.

I'm working on moving a client's repository from a "makeshift monorepo" to a real `yarn`/`lerna` driven monorepo. They make heavy use of `NodejsFunction`, so I'm moving them to the newer [reference project architecture](https://docs.aws.amazon.com/cdk/api/latest/docs/aws-lambda-nodejs-readme.html#reference-project-architecture) with a single lockfile at the root of the repository.

While working through this issue, I kept running into this error message:

```
> yarn cdk diff
Bundling asset SomeLambdaHandler/SomeSubLambda/Lambda/Code/Stage...
Usage Error: Couldn't find a script named "esbuild".

$ yarn run [--inspect] [--inspect-brk] <scriptName> ...
Failed to bundle asset SomeLambdaHandler/SomeSubLambda/Lambda/Code/Stage, bundle output is located at /Users/blimmer/code/client/project/packages/some-workspace/cdk.out/bundling-temp-2f3ffba54d828547eb851ebe672a601943e153ec31fdc5e45f8e80ed976da6d3-error: Error: bash exited with status 1
Subprocess exited with error 1
```

This was confusing to me because I have `esbuild` installed in both sub-packages that require it. The error message just tells me that `bash` failed to run, which isn't very helpful.

However, when I set an interactive breakpoint, I got a lot more information about the failure. By digging into these arguments https://github.com/aws/aws-cdk/blob/507769aa034ba3d8daa497953be629408072baed/packages/%40aws-cdk/aws-lambda-nodejs/lib/util.ts#L56-L57 I can actually see what's being run and which directory it's run in.

| argument | contents | comments |
| -------- | -------- | -------- |
| `cmd`    | `bash`   | this doesn't really tell me anything about what's happening |
| `args`   | [ `-c`, `"yarn run esbuild --bundle \"/Users/blimmer/code/client/project/packages/some-workspace/lib/some-sub-lambda/lambda/index.ts\" --target=node14 --platform=node --outfile=\"/Users/blimmer/code/client/project/packages/some-workspace/cdk.out/bundling-temp-2f3ffba54d828547eb851ebe672a601943e153ec31fdc5e45f8e80ed976da6d3/index.js\" --external:aws-sdk"` ] | the second argument of this array actually represents the command being run - this is way more useful than just `bash` |
| `options` | `{ ...lotsOfOtherStuff, cwd: '/Users/blimmer/code/client/project' }` | `cwd` was actually crucial for me to fix this problem. because I see this is running in the root of the monorepo, it shows that I need to install `esbuild` there, instead of in the workspaces. |

----

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

This PR improves the error message when a lambda-nodejs function fails to bundle.

I'm working on moving a client's repository from a "makeshift monorepo" to a real `yarn`/`lerna` driven monorepo. They make heavy use of `NodejsFunction`, so I'm moving them to the newer [reference project architecture](https://docs.aws.amazon.com/cdk/api/latest/docs/aws-lambda-nodejs-readme.html#reference-project-architecture) with a single lockfile at the root of the repository.

While working through this issue, I kept running into this error message:

```
> yarn cdk diff
Bundling asset SomeLambdaHandler/SomeSubLambda/Lambda/Code/Stage...
Usage Error: Couldn't find a script named "esbuild".

$ yarn run [--inspect] [--inspect-brk] <scriptName> ...
Failed to bundle asset SomeLambdaHandler/SomeSubLambda/Lambda/Code/Stage, bundle output is located at /Users/blimmer/code/client/project/packages/some-workspace/cdk.out/bundling-temp-2f3ffba54d828547eb851ebe672a601943e153ec31fdc5e45f8e80ed976da6d3-error: Error: bash exited with status 1
Subprocess exited with error 1
```

This was confusing to me because I have `esbuild` installed in both sub-packages that require it. The error message just tells me that `bash` failed to run, which isn't very helpful.

However, when I set an interactive breakpoint, I got a lot more information about the failure. By digging into these arguments https://github.com/aws/aws-cdk/blob/507769aa034ba3d8daa497953be629408072baed/packages/%40aws-cdk/aws-lambda-nodejs/lib/util.ts#L56-L57 I can actually see what's being run and which directory it's run in.

| argument | contents | comments |
| -------- | -------- | -------- |
| `cmd`    | `bash`   | this doesn't really tell me anything about what's happening |
| `args`   | [ `-c`, `"yarn run esbuild --bundle \"/Users/blimmer/code/client/project/packages/some-workspace/lib/some-sub-lambda/lambda/index.ts\" --target=node14 --platform=node --outfile=\"/Users/blimmer/code/client/project/packages/some-workspace/cdk.out/bundling-temp-2f3ffba54d828547eb851ebe672a601943e153ec31fdc5e45f8e80ed976da6d3/index.js\" --external:aws-sdk"` ] | the second argument of this array actually represents the command being run - this is way more useful than just `bash` |
| `options` | `{ ...lotsOfOtherStuff, cwd: '/Users/blimmer/code/client/project' }` | `cwd` was actually crucial for me to fix this problem. because I see this is running in the root of the monorepo, it shows that I need to install `esbuild` there, instead of in the workspaces. |

----

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