Add CMake support to cpp module

[filippobrizzi]

Public-Facing Changes

None

Description

Add CMake support for the top-level cpp module.

This allows to use mcap in projects that do not support/use conan.

The CMake file generates the install config files that allow running find_package(mcap) in external projects.

NOTES:

• It is possible to update examples/ and test/ to be part of the global CMake and stop using conan to build them.
  • If this is needed, I can do it in this PR.
• I haven't updated the README, as soon as I get greenlight for this PR I will do it.

[CLAassistant]

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✅ filippobrizzi
❌ Filippo Brizzi

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[filippobrizzi]

PTAL @jtbandes @wkalt @james-rms

[indirectlylit]

Hi @filippobrizzi, thank you for the contribution! Improved support for our CMake users is important to us. It may be a little while before we get to this, and we appreciate your patience in the meantime.

One thing that will be necessary eventually is a CI step.

At a high level, we'd like to provide CMake scaffolding for folks to build off of without maintaining something for all architectures and environments. It's possible that we could even migrate from conan to cmake internally if we can do it in a way that doesn't impact existing conan users.

Any feedback would be appreciated!

[filippobrizzi]

using latest ubuntu to get latest cmake version needed to create an interface library

[filippobrizzi]

Hi @indirectlylit thanks for the reply.
I have done the following as a demonstration of a possible solution:

• mcap/cpp is an header only library so there is nothing much to test here as nothing compile
• to test that the CMake is correct I updated test to be compiled via CMake and fix CI to work with the new paths.
• examples still work with conan, in this way in CI we make sure that conan still works and as a demonstration on how to use it.
• overall we have conan and cmake working side-by-side without any issue.

The only real design choice that I made here for the CMake solution is that lz4 and zstd are imported and built only if tests are enabled. The reason is that I think it should be left to the user the decision whether to use and how to import them. And the test CMakeLists.txt shows how that could be done.
Please take a look and let me know what you think. Happy to provide extra feedback and explanation

[indirectlylit]

Thank you @filippobrizzi - iterating on Github CI code can be frustrating and I appreciate the effort!

I've created internal tracking issue FG-6815 to make sure this stays on our radar and we'll review asap.