Auto merge of #38840 - kjaleshire:multiple-targets-error-fix, r=nrc

Warn that the link target ignores the given name

Hi, new contributor here. This is my stab at #20130, any feedback welcome!

Author: bors

src/librustc_driver/driver.rs

@@ -1334,9 +1334,10 @@ pub fn build_output_filenames(input: &Input,
                                            .values()
                                            .filter(|a| a.is_none())
                                            .count();
-            let ofile = if unnamed_output_types > 1 {
-                sess.warn("ignoring specified output filename because multiple outputs were \
-                           requested");
+            let ofile = if unnamed_output_types > 1 &&
+                            sess.opts.output_types.contains_key(&OutputType::Exe) {
+                sess.warn("ignoring specified output filename for 'link' output because multiple \
+                           outputs were requested");
                 None
             } else {
                 Some(out_file.clone())