[compiler-rt] [builtins][CMake] Replace custom target for lse_builtin symlinks (PR #66936)

[Petr Hosek via llvm-commits]

petrhosek wrote:

> The only thing that stood out to me on that same page was:
> 
> > Each source file may have at most one command specifying it as its main dependency.
> 
> Which we're violating. Dunno if it matters in practice, but we could just use `DEPENDS` instead?

Thanks for catching that, I missed this part. I changed `MAIN_DEPENDENCY` to `DEPENDS`.

https://github.com/llvm/llvm-project/pull/66936