Revert "Just checking if #[link] are applied at all"

This reverts commit a2bd198.

Author: Minoru

src/unix/mod.rs

@@ -345,6 +345,9 @@ cfg_if! {
         extern {}
     } else if #[cfg(any(target_os = "macos",
                         target_os = "ios"))] {
+        #[link(name = "c")]
+        #[link(name = "m")]
+        #[link(name = "iconv")]
         extern {}
     } else if #[cfg(any(target_os = "android",
                         target_os = "openbsd"))] {