[lld] [LLD] [MinGW] Ignore the -rpath option (PR #102886)

[Fangrui Song via llvm-commits]

MaskRay wrote:

lld/COFF prints warnings for unknown options. Therefore, if `-rpath` is unrecognized, printing a warning seems reasonable.

(I'm actually surprised that the PE/COFF port uses warnings instead of errors (ELF, wasm, Mach-O)....)

https://github.com/llvm/llvm-project/pull/102886