CMake: Add RERUN_INSTALL_RERUN_C option to disable installation of rerun_c library

[traversaro]

When building the C++ SDK with the BUILD_SHARED_LIBS option set to ON, it is not compulsory to also install the rerun_c static library. This PR adds a CMake option RERUN_INSTALL_RERUN_C (enabled by default), that can be disabled when rerun_sdk is not compiled as static library.

This is useful when packaging the rerun C++ SDK if you want to avoid to also install the rerun_c static library (related to #4579).

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[traversaro]

Apparently one CI check is failing due to a missing label, but I can't add labels.

[Wumpf]

thank you! I figured there's no harm in always installing rerun_c, but sure no reason to not make it configurable.

CI for non-maintainer contributors has some issues right now, we'll look after it

[traversaro]

I figured there's no harm in always installing rerun_c, but sure no reason to not make it configurable.

Thanks!

Just to provide a bit more of context related of how this is related to #4579 . For various reasons (that may be a bit long to discuss here, for the curious I recently discussed this in PickNikRobotics/RSL#116 (comment)) many Linux distributions and/or C++/multi language package managers prefer to avoid to distribute static libraries, in particular conda-forge (see https://github.com/conda-forge/cfep/blob/main/cfep-18.md) prefers to avoid static libraries, mainly because as soon as you have a static library with C or C++ linkage, you do not have all the great mangling that Rust does to ensure to avoid collisions between incompatible symbols (see conda-forge/staged-recipes#23725 (comment)). One could think of just shipping rerun_c and let users ignore it, but if you start shipping it, by Hyrum's Law eventually users will depend on it, so as it is harmless not to include it in the packages, we prefer to do that.