Explicitly check that we are looking at GNU ld, and otherwise skip th…

…e check.

(The first version of the PR had this implicitly by always searching for the
string literal "GNU ld version " when looking for where to start the search for
the version number.)

src/librustc_codegen_ssa/back/link.rs

@@ -541,6 +541,12 @@ fn check_for_buggy_ld_version(sess: &Session,
     };
     debug!("check_for_buggy_ld_version first_line: {:?}", first_line);
 
+    if !first_line.contains("GNU ld") {
+        // If we cannot find "GNU ld" in the version string, then assume that
+        // this is not actually GNU ld; no need for warning.
+        return;
+    }
+
     let version_suffix_start = match first_line.find(" 2.") {
         None => {
             // if we cannot find ` 2.`, then assume that this an ld version that