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

This is one of the most common issues new users face, especially as so
many reccomended CMake configurations include `-DLLVM_ENABLE_LLD=ON`.

I don't want the error message to get too long but let's at least say
that there are 2 main reasons for the failure. If it's not those then
maybe folks will find the actual problem while trying to discount them.

The new message looks like:
```
CMake Error at cmake/modules/HandleLLVMOptions.cmake:330 (message):
  Host compiler does not support '-fuse-ld=not_a_linker'.  Please make sure
  that 'not_a_linker' is installed and that your host compiler can compile a
  simple program when given the option '-fuse-ld=not_a_linker'.
Call Stack (most recent call first):
  CMakeLists.txt:910 (include)
```