[cmake] Switch FATAL_ERROR to SEND_ERROR

It's possible for multiple distribution components to have missing
targets, and it's a lot more convenient to get all those errors in one
shot rather than having to fix them individually.

llvm-svn: 317148
GitOrigin-RevId: 909f5c9b7c81c600ba8a80c45f60717a61b31dc0
1 file changed