[clang] [Clang][NFC] Remove '--' separator in the linker wrapper usage (PR #84253)

[Fangrui Song via cfe-commits]

MaskRay wrote:

If a LLVMOption users needs to parse `--`, DashDashParsing from https://reviews.llvm.org/D152286 is better :)

https://github.com/llvm/llvm-project/pull/84253