[llvm] [llvm][CMake] Expand error message shown when -fuse-ld= test fails (PR #66778)

[David Spickett via llvm-commits]

DavidSpickett wrote:

The other way to do this is adding the information to https://llvm.org/docs/CMake.html#llvm-use-linker, but it's not as immediate. I could do both if it helps to have something to cite in answers.

https://github.com/llvm/llvm-project/pull/66778