--sourcemap flag does not generate sourcemaps

[MannyAdumbire]

Describe the bug

I'm no longer about to get sourcemaps when using the --sourcemap flag.
This used to work ( last year) - 10up-toolkit build --sourcemap

The only thing that works now for our project is adding "sourcemap": true, as described here https://github.com/10up/10up-toolkit/blob/develop/packages/toolkit/README.md#production-sourcemaps. That's not ideals because we only want the sourcemap for development builds.

Thanks for any advice!

Steps to Reproduce

Run from within WordPress project, run 10up-toolkit build --sourcemap.

Screenshots, screen recording, code snippet

No response

Environment information

No response

WordPress information

wp-core

version: 6.9

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