[clang] clang-linker-wrapper/LinkerWrapperOpts.td: "--sysroot" => "--sysroot=" (PR #65313)

[Fangrui Song via cfe-commits]

https://github.com/MaskRay approved this pull request.

Long options separated by a space are not common and newer driver options prefer `=`. There is no compatibility concern for this internal tool spawned by clang. So LGTM

https://github.com/llvm/llvm-project/pull/65313