`bazel build ...` failed when a sub folder contains another bazel project and has been built firstly

### Description of the bug:

[Bazel document](https://bazel.build/concepts/build-ref#workspace) says that a bazel project in a sub folder will be ignored.
However, I found it's not always true.
I have a bazel project with a sub folder contains another bazel project. The build `bazel build ...` failed if the bazel project in the sub folder was built first.

> bazel build ...
ERROR: Skipping '...': error loading package under directory '': error loading package 'foo/bazel-foo/external/bazel_tools/src/main/protobuf': Label '//third_party/grpc/bazel:cc_grpc_library.bzl' is invalid because 'third_party/grpc/bazel' is not a package; perhaps you meant to put the colon here: '//:third_party/grpc/bazel/cc_grpc_library.bzl'?
WARNING: Target pattern parsing failed.
ERROR: error loading package under directory '': error loading package 'foo/bazel-foo/external/bazel_tools/src/main/protobuf': Label '//third_party/grpc/bazel:cc_grpc_library.bzl' is invalid because 'third_party/grpc/bazel' is not a package; perhaps you meant to put the colon here: '//:third_party/grpc/bazel/cc_grpc_library.bzl'?
INFO: Elapsed time: 0.485s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (5 packages loaded)
currently loading: foo/bazel-foo/external/bazel_tools/src/main/protobuf

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

1. issue `bazel build ...` in folder foo, should succeed
2. issue `bazel build ...` in root folder, should fail

```shell
tree .
.
├── BUILD
├── empty.cc
├── foo
│ ├── BUILD
│ ├── empty.cc
│ └── WORKSPACE
└── WORKSPACE
```

### Which operating system are you running Bazel on?

Ubuntu

### What is the output of `bazel info release`?

release 6.2.1

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

_No response_

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

_No response_

### Is this a regression? If yes, please try to identify the Bazel commit where the bug was introduced.

_No response_

### Have you found anything relevant by searching the web?

Not found a similar issue on github issues.

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

_No response_

Reproduce the issue from the provided tree using the root and foo BUILD and WORKSPACE files: run `bazel build ...` in foo first, then from the root. Compare the package-loading behavior and the reported external bazel_tools path; done means the root build succeeds after the nested project has been built.

Written by the indexing model from the issue text.