[skip changelog] Github Actions bugfixes

[rsora]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests before creating one)
• The PR follows our contributing guidelines

• What kind of change does this PR introduce?

  • Bugfix: Replace $PWD with github actions workspace variable to solve invalid chars issue in container volume binding (https://github.com/arduino/arduino-cli/runs/569994650?check_suite_focus=true#step:3:65)
  • Bugfix: Add semver tool to enable pre-release flag in release creation. We lost this bit of functionality (Explicit support for semantic versioning pre-releases. actions/create-release#9) when we moved the github release creation from goreleaser to github actions
  • Refactoring: Removed get_tag step in release workflow, adding the tag parse directly in Notarize binary step

• What is the current behavior?
  Nightly and Release workflow fail

• What is the new behavior?
  Release workflow now supports pre-releases automatically again

• Does this PR introduce a breaking change?
  No

• Other information:

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