Disable the cmsg test on Windows

Author: asomers

libc-test/build.rs

@@ -5,11 +5,15 @@ extern crate ctest;
 
 use std::env;
 
+#[cfg(unix)]
 fn do_cc() {
     cc::Build::new()
         .file("src/cmsg.c")
         .compile("cmsg");
 }
+#[cfg(not(unix))]
+fn do_cc() {
+}
 
 fn do_ctest() {
     let target = env::var("TARGET").unwrap();

libc-test/test/cmsg.rs

@@ -3,6 +3,9 @@
 
 extern crate libc;
 
+#[cfg(unix)]
+mod t {
+
 use libc::{c_uchar, c_uint, c_void, cmsghdr, msghdr};
 use std::mem;
 
@@ -92,3 +95,5 @@ fn test_cmsg_space() {
         }
     }
 }
+
+}