Software compatibility and our own "User-Agent" problem
The problem that the people working on FreeBSD found is that if they tried to run configure in an environment in which lld is installed as the standard linker, lld would be determined by configure as if it were an ancient Unix linker like 30 years ago. Further investigation revealed that the configure script runs the linker in the background with the --help option, and determines it as a modern linker only when the displayed help message contains “GNU” or “with BFD”. What this means is that only GNU linkers are considered modern in the environment, and all the other linkers are considered terribly outdated.
When life gives you autotools...