rustbuild: Build tests with LLD if `use-lld = true` was passed (non-msvc)

src/bootstrap/test.rs

@@ -1067,10 +1067,16 @@ fn run(self, builder: &Builder<'_>) {
 
         let mut hostflags = flags.clone();
         hostflags.push(format!("-Lnative={}", builder.test_helpers_out(compiler.host).display()));
+        if builder.config.use_lld && !compiler.host.triple.contains("msvc") {
+            hostflags.push("-Clink-args=-fuse-ld=lld".to_string());
+        }
         cmd.arg("--host-rustcflags").arg(hostflags.join(" "));
 
         let mut targetflags = flags;
         targetflags.push(format!("-Lnative={}", builder.test_helpers_out(target).display()));
+        if builder.config.use_lld && !target.contains("msvc") {
+            targetflags.push("-Clink-args=-fuse-ld=lld".to_string());
+        }
         cmd.arg("--target-rustcflags").arg(targetflags.join(" "));
 
         cmd.arg("--docck-python").arg(builder.python());