What

• Fixes Investigate whether we can build arrow-cpp from source in C++ #4028

Confirmed to be working on Linux, Mac and Windows. On windows also made sure this works with debug runtime and experimented a bit with Visual Studio setups. Also checked Windows against the external sample, see rerun-io/cpp-example-opencv-eigen#8

Made improvements to our CMakeLists files overall. Notably we no longer need DOWNLOAD_EXTRACT_TIMESTAMP ON to suppress warnings - idea from rerun-io/cpp-example-opencv-eigen#6, setting a range for the cmake version fixes it

Drawbacks:

• LOTS of cmake log spam during build
• a bit longer builds on the first run, seems to be a bit more pronounced on Windows (no hard numbers available yet)

Advantages:

• no longer needed to install libarrow
• works on Windows debug builds (note that other libraries like OpenCV might still have this issue)
• stable against all c++ library/compiler changes, no fear of weird runtime errors because of stdlib mismatches
• more lightweight artifacts - on Windows one would have needed to ship a large number of dlls, now none

It's still worth considering if we should ship prebuilt debug & release arrow dlls instead.

TODO: We need to document this new behavior and how to turn it off in the respective doc pages. By default the user no longer needs to install libArrow with this.

Important CMake options that need documenting (can partially copy& paste this!):

• RERUN_ARROW_LINK_SHARED
  • exited before but now it's default OFF (EDIT:) on windows. This makes it easier to relocate windows executable (don't need to copy Arrow.dll around!). EDIT: On mac this made the address sanitizer crazy for me and I reckon it's an unnecessary slowdown
• RERUN_ARROW_EXTERNAL_PROJECT (new!)
  • Default on
  • If enabled we download Arrow 10.0.1 and build it in a as small as possible fashion
  • If disabled we run find_package == old behavior
• RERUN_C_LIB
  • where to find the static c library that rerun_sdk links against
  • in repo defaults to cargo built
  • outside repo defaults to /lib/ folder + platform artifact name

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested demo.rerun.io (if applicable)
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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