When running the ABI checker from the build artifact, the executable
should be able to find baselines in the same relative paths as if
it's running from a toolchain.
CMake supports the notion of installation components. Right now we have some
custom code for supporting swift components. I think that for installation
purposes, it would be nice to use the CMake component system.
This should be a non-functional change. We should still only be generating
install rules for targets and files in components we want to install, and we
still use the install ninja target to install everything.
