Don't hash shared libraries for cache key

[ChrisBr]

Shared libraries often contain timestamps of when they were compiled and other non-stable data
hence would often produce different hashes on different machines. This happens often in our CI.

Related to #8633

cc @casperisfine

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[ChrisBr]

I'm not sure the failed tests are related 🤔

[casperisfine]

Hum, actually when we hash the .rb files, we don't care where they are located. So using the path as a "digest" mean that the BUNDLE_PATH now has influence, that may also be a problem for some cases. Maybe we should just extract a small name, e.g. Zlib.crc32(File.basename(path)).to_s.

[ChrisBr]

Yeah good point.

[jonas054]

Looks good to me, regarding the changed functionality. I had some minor comments.

[ChrisBr]

♻️ @jonas054 please have another look

[bbatsov]

Hmm, lots of tests are currently failing.

[ydah]

Looks like there are some RuboCop offense in lib/rubocop/result_cache.rb

Run bundle exec rake internal_investigation
RuboCop failed!
Running RuboCop...
Inspecting 1403 files
........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................W..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Offenses:

lib/rubocop/result_cache.rb:208:9: C: [Correctable] Layout/IndentationWidth: Use 2 (not -8) spaces for indentation.
        File.basename(path)
        ^^^^^^^^
lib/rubocop/result_cache.rb:209:7: C: [Correctable] Layout/ElseAlignment: Align else with if.
      else
      ^^^^
lib/rubocop/result_cache.rb:211:7: W: [Correctable] Layout/EndAlignment: end at 211, 6 is not aligned with if at 205, 16.
      end
      ^^^

1[40](https://github.com/rubocop/rubocop/runs/7642059901?check_suite_focus=true#step:8:41)3 files inspected, 3 offenses detected, 3 offenses autocorrectable
Error: Process completed with exit code 1.

[ChrisBr]

Hmm, lots of tests are currently failing.

Fixed my Rubocop violation and rebased on latest master but seems there are still some broken in CI / RSpec 4 (pull_request). I don't think it's related to the changes in this PR though (if so I would appreciate some pointers how I can reproduce this locally, I did run bundle exec rake default which passed).

[koic]

Thanks!