backport rust-lang#623

Author: XrXr

build.rs

@@ -513,10 +513,6 @@ mod c {
                 ("__fe_getround", "fp_mode.c"),
                 ("__fe_raise_inexact", "fp_mode.c"),
             ]);
-
-            if target_os != "windows" {
-                sources.extend(&[("__multc3", "multc3.c")]);
-            }
         }
 
         if target_arch == "mips" {