Build fails for x86_64-linux-android

[mattico]

https://travis-ci.org/rust-lang-nursery/rustup.rs/jobs/261063687#L1537

error[E0308]: mismatched types
  --> target/cargo-home/registry/src/github.com-1ecc6299db9ec823/net2-0.2.30/src/socket.rs:40:51
   |
40 |             ::cvt(c::bind(self.inner.raw(), addr, len as len_t)).map(|_| ())
   |                                                   ^^^^^^^^^^^^ expected i32, found u32

I assume the fix is just to

-#[cfg(all(target_arch = "aarch64",target_os = "android"))]
+#[cfg(all(any(target_arch = "aarch64", target_arch = "x86_64"),target_os = "android"))]
use libc::c_int as len_t;

I'll see if that works locally.