Preventing concurrency bugs by making the loadOnce field of walkConfig a
pointer to sync.Once to avoid instead copying the mutex within it.

Fixes #1531

Co-authored-by: Fabian Meumertzheim <fabian@meumertzhe.im>

Fixes #1532

Co-authored-by: Fabian Meumertzheim <fabian@meumertzhe.im>

)

…1553)

* Add test

* Add to default_gazelle_overrides.bzl

* diff: do not use the epoch as timestamp

* Fix tests

* Update comment to mention epoch is special

The build file generation logic works like this today:

```
GenerateRules()
  package.go->*goTarget.addFiles
  package.go->getPlatformStringsAddFunction()
  fileinfo.go->isOSArchSpecific()
```

Depending on whether the file has special Go build directives, Gazelle
would use a different logic to include/exclude the file into the 'srcs'
attribute of the Go targets.

In #1512, we added support for 'unix' build directive but did not tell
Gazelle to treat files with 'unix' file as OS specific file. This caused
Gazelle to mismatch the OS in a later stage and exclude the needed file
instead.

Fix that logic and provide some additional tests to reinforce the
fileinfo logic.

Also added a small knob to print stdout of Gazelle when it's run under
go_repository with `debug_mode` attribute set to True.  Most Gazelle's
logs are printed to stdout and not stderr.

The constraint labels emitted as `select` keys now use the apparent name
of the `rules_go` repository when using Bzlmod, with a fallback to
`io_bazel_rules_go` if the `rules_go` module is not a declared
`bazel_dep`.

* Let `bazel_dep`s replace Go deps

When a Go dependency is brought in both as a `bazel_dep` and as a
regular Go dependency via e.g. go.mod, the `bazel_dep` repo should be
used instead of creating a separate `go_repository`, which would risk
duplicate packages.

This is realized by registering every Bazel module with a
`go_deps.from_file` tag as providing the Go module of the same version
with the module path given in `go.mod`.

Gazelle is aware of these tags and generates either a canonical label or
 a label using the apparent module repo name (the latter only for the
root module and only if it directly depends on the `bazel_dep`).

* Add warning

* Add support for relaxed semvers

* Add a dep on circl