Add a libtrixi cmake module

[benegee]

Resolves #121

[sloede]

Thanks for getting started on this. I think it would be great if we could also provide a test for this, e.g., if we add a CMakeLists.txt that shows how to build one of the examples against an existing libtrixi installation.

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (e165220) 98.05% compared to head (d7169d1) 98.05%.

❗ Current head d7169d1 differs from pull request most recent head 3427bec. Consider uploading reports for the commit 3427bec to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #132   +/-   ##
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  Coverage   98.05%   98.05%           
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  Files          13       13           
  Lines         565      565           
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  Hits          554      554           
  Misses         11       11           

Flag	Coverage Δ
unittests	98.05% <ø> (ø)

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[sloede]

I haven't looked at it in detail, but we should add a test where the external CMakeLists.txt is actually used to build an example executable. Otherwise it is likely that the script will not work anymore at some point (see the Doxygen example from a few days ago 😬)

[sloede]

This looks very, very good imho, thanks a lost! Just one thought:
Right now, there is a lot of copy pasting in the CI such that a user does not just see what needs to be done from looking at the example CMakeLists.txt alone. Therefore, I suggest to

• get rid of the copy paste stuff and
• add a build.sh file that encapsulates the remaining commands.

That way, everything is tested in CI and nothing is "hidden" in some CI yml file.

I tried to implement this as suggestions, but I think there might be some things I missed.

[sloede]

LGTM, with just one more (small) comment left

[sloede]

LGTM! Great work!