CMake Error: FATAL_ERROR v. SEND_ERROR
message(FATAL_ERROR) will stop processing a project immediately while
message(SEND_ERROR) will continue processing but exit with an error at the end. However, many of the errors builtin to CMake's commands, such as include() failure, have no way to make them fatal.
We should consider adding some way to activate immediate termination on the first error of any kind. Or, perhaps we should even add a policy to make builtin command errors fatal always.