Commandline compatibility with Clang?

[Kagamin via digitalmars-d-ldc]

On Thursday, 22 October 2015 at 19:16:00 UTC, Kai Nacke wrote:
> There are 2 reasons for the naming of command line options. 
> First, ldc predates Clang. Second, ldc links against LLVM and 
> inherits all the command line options which are also not 
> compatible with Clang.

How is that? AFAIK all llvm tools use gcc-like -o option.