linker: Remove special case for rust-lld in detect_self_contained_mingw

`rust-lld` is supposed to live in sysroot, so it doesn't change the behavior of the function, only removes a potential micro-optimization.

Author: petrochenkov

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1763,10 +1763,6 @@ fn link_output_kind(sess: &Session, crate_type: CrateType) -> LinkOutputKind {
 
 // Returns true if linker is located within sysroot
 fn detect_self_contained_mingw(sess: &Session, linker: &Path) -> bool {
-    // Assume `-C linker=rust-lld` as self-contained mode
-    if linker == Path::new("rust-lld") {
-        return true;
-    }
     let linker_with_extension = if cfg!(windows) && linker.extension().is_none() {
         linker.with_extension("exe")
     } else {