subsecond/cli: fix linker and passing through -fuse-ld properly (#4222)

* subsecond/cli: fix passing through -fuse-ld for LinkerFlavour::Gnu

* if linker isn't a relative, local path, keep it unresolved since its a command on PATH

packages/cli/src/build/request.rs

@@ -1488,6 +1488,7 @@ impl BuildRequest {
                         || arg.starts_with("-m")
                         || arg.starts_with("-Wl,--target=")
                         || arg.starts_with("-Wl,-fuse-ld")
+                        || arg.starts_with("-fuse-ld")
                     {
                         out_args.push(arg.to_string());
                     }