local_repository() pointing into workspace is not invalidated when external repo file checking is disabled.

Description of the bug:

Hi!

I noticed that our warm Bazel implementation started complaining about inconsistent file sizes in @@+local_repository+blah//, when someone edited //third_party/blah/BUILD. It turns out that this repo was configured as

local_repository(
    name = "blah",
    path = "third_party/blah",
)

We are running with --watchfs --experimental_check_external_repository_files=false.

I am 99% sure that this problem is caused by --noexperimental_check_output_files not specially treating external repositories that point back into the source tree.

My gut feeling is that making this work will be hard, and I wonder if we could instead forbid this?

Which category does this issue belong to?

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

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Which operating system are you running Bazel on?

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What is the output of bazel info release?

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

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

If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

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Have you found anything relevant by searching the web?

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

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