Skip bundler self-checksum for unreleased bundlers (#9501)

* Skip bundler self-checksum for unreleased bundlers

Using `Bundler.gem_version.end_with?(".dev")` only skips the own
checksum on master, but patch releases run from a source checkout
(e.g., bumping bundler/lib/bundler/version.rb to 4.0.11 on a release
branch) still record the checksum, which is environment dependent on
the local gem cache and causes frozen-lock drift on CI.

Generalize the guard with `released_bundler?`, which returns false for
any prerelease version and for bundlers loaded outside of an installed
gem location (`/specifications/`), so dev workflows don't record
self-checksums while released installs still do.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Revert "Skip bundler self-checksum for unreleased bundlers"

This reverts commit d4e51dd.

* Skip bundler checksum when running version:update_locked_bundler:

- Our development lockfile should not include the checksum of bundler
  itself. No matter if we are doing a release.
  The problem being that including a checksum in our development
  lockfile create issues as some rake tasks don't run the same way on
  CI.

  For example, some rake tasks, build bundler.gem and some other
  don't. I explained in more details the issue here 2c40b8d

  This commit here is motivated by the fact that when the release
  manager runs `version:update_locked_bundler`, if a
  `bundler-<VERSION>.gem` exists on its system (e.g it previously ran
  `rake bundler:install`), then the lockfile will include a checksum
  entry.

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Edouard CHIN <chin.edouard@gmail.com>

Author: 3 people

Rakefile

@@ -32,6 +32,7 @@ namespace :version do
   task :update_locked_bundler do |_, _args|
     stdout = Spec::Rubygems.dev_bundle "--version"
     version = stdout.split(" ").last
+    ENV["SKIP_BUNDLER_CHECKSUM"] = "1"
 
     Dir.glob("{tool/bundler/*_gems.rb,spec/realworld/fixtures/*/Gemfile}").each do |file|
       Spec::Rubygems.dev_bundle("lock", "--update", "--bundler", version, gemfile: file)

bundler/lib/bundler/lockfile_generator.rb

@@ -103,7 +103,7 @@ def add_section(name, value)
     end
 
     def bundler_checksum
-      return [] if Bundler.gem_version.to_s.end_with?(".dev")
+      return [] if Bundler.gem_version.to_s.end_with?(".dev") || ENV["SKIP_BUNDLER_CHECKSUM"]
 
       bundler_spec = definition.sources.metadata_source.specs.search(["bundler", Bundler.gem_version]).last
       return [] unless File.exist?(bundler_spec.cache_file)