target.contains -> target_os ==

build.rs

@@ -221,7 +221,7 @@ fn main() {
                 sources.extend(&["x86_64/floatdidf.c", "x86_64/floatdisf.c", "x86_64/floatdixf.c"]);
             }
         } else {
-            if target_os != "freebsd" && !target.contains("netbsd") {
+            if target_os != "freebsd" && target_os != "netbsd" {
                 sources.extend(&["gcc_personality_v0.c"]);
             }