Description of the bug:

Setting the --enable_bzlmod flag (even with an empty MODULE.bazel file) breaks toolchain resolution for toolchains registered in the WORKSPACE file.

What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

https://github.com/gregmagolan/repro-enable_bzlmod_breaks_workspace

Which operating system are you running Bazel on?

MacOS

What is the output of bazel info release?

release 6.0.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

https://github.com/gregmagolan/repro-enable_bzlmod_breaks_workspace

Have you found anything relevant by searching the web?

Searched through Bazel issues and didn't see any duplicates.

Any other information, logs, or outputs that you want to share?