fix workflows for external PRs

[skjerns]

this should hopefully enable our test suit for PRs from forked repos

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (246c76e) 80.75% compared to head (8388bdf) 80.75%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #206 +/- ## ======================================= Coverage 80.75% 80.75% ======================================= Files 3 3 Lines 795 795 Branches 169 169 ======================================= Hits 642 642 Misses 112 112 Partials 41 41 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `80.75% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Holger+Nahrstaedt#carryforward-flags-in-the-pull-request-comment) to find out more.

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