Don't fail fast

It's a nightly, better use the time to check the whole thing on all
configurations.

Unfortunately, with "continue-on-error: true" GitHub actions will still
mark the workflow run as successful even if all the steps fail. However,
we'd like to run Cppcheck even if clang-tidy gets errors.

Not possible, it's a limitation of GitHub actions documented in:
 - actions/runner#2347
 - https://github.com/orgs/community/discussions/15452

GitHub folks collected feedback for this over a year ago:
https://github.com/orgs/community/discussions/15452#discussioncomment-5184613

but it's still not fixed.

.github/workflows/nightly.yml

@@ -27,6 +27,7 @@ jobs:
           - name: Windows
             os: windows-2022
             tidy-executble: clang-tidy
+      fail-fast: false
     continue-on-error: true
 
     steps: