Collect all possible LLVM_DISTRIBUTION_COMPONENTS for a given
configuration, and store them in LLVM_ALL_DISTRIBUTION_COMPONENTS cache
variable. This will make it easier for distribution maintainers to
establish the possible options, and to update them on upgrades.
This isn't really possible to do because CMake doesn't have a mechanism for listing all targets. A more correct approach for this would require generating a ninja build, then you could use ninja -t list to dump all the targets, then you can post-process that list to find a full list of components.