Expose IP_PKTINFO Control Message on Android

The commit nix-rust#1222 added the very
useful Ipv4PktInfo to allow `sendmsg` to define the origin of the ip.

Unfortunattely, it didn't add the struct to Android target devices as
well. This commit adds the `target_os = "android"` checks on the same
place to allow the compilation to work for the following archs tested:

- `cross build --target aarch64-linux-android`
- `cross build --target x86_64-linux-android`
- `cross build --target armv7-linux-androideabi`

src/sys/socket/mod.rs

@@ -724,7 +724,8 @@ pub enum ControlMessage<'a> {
     /// [`ip(7)`](http://man7.org/linux/man-pages/man7/ip.7.html) man page.
     #[cfg(any(target_os = "linux",
               target_os = "macos",
-              target_os = "netbsd"))]
+              target_os = "netbsd",
+              target_os = "android"))]
     Ipv4PacketInfo(&'a libc::in_pktinfo),
 
     /// Configure the sending addressing and interface for v6
@@ -734,7 +735,8 @@ pub enum ControlMessage<'a> {
     #[cfg(any(target_os = "linux",
               target_os = "macos",
               target_os = "netbsd",
-              target_os = "freebsd"))]
+              target_os = "freebsd",
+              target_os = "android"))]
     Ipv6PacketInfo(&'a libc::in6_pktinfo),
 }
 
@@ -818,10 +820,11 @@ impl<'a> ControlMessage<'a> {
                 gso_size as *const _ as *const u8
             },
             #[cfg(any(target_os = "linux", target_os = "macos",
-                      target_os = "netbsd"))]
+                      target_os = "netbsd", target_os = "android"))]
             ControlMessage::Ipv4PacketInfo(info) => info as *const _ as *const u8,
             #[cfg(any(target_os = "linux", target_os = "macos",
-                      target_os = "netbsd", target_os = "freebsd"))]
+                      target_os = "netbsd", target_os = "freebsd",
+                      target_os = "android"))]
             ControlMessage::Ipv6PacketInfo(info) => info as *const _ as *const u8,
         };
         unsafe {
@@ -864,10 +867,11 @@ impl<'a> ControlMessage<'a> {
                 mem::size_of_val(gso_size)
             },
             #[cfg(any(target_os = "linux", target_os = "macos",
-              target_os = "netbsd"))]
+              target_os = "netbsd", target_os = "android"))]
             ControlMessage::Ipv4PacketInfo(info) => mem::size_of_val(info),
             #[cfg(any(target_os = "linux", target_os = "macos",
-              target_os = "netbsd", target_os = "freebsd"))]
+              target_os = "netbsd", target_os = "freebsd",
+              target_os = "android"))]
             ControlMessage::Ipv6PacketInfo(info) => mem::size_of_val(info),
         }
     }
@@ -886,10 +890,11 @@ impl<'a> ControlMessage<'a> {
             #[cfg(target_os = "linux")]
             ControlMessage::UdpGsoSegments(_) => libc::SOL_UDP,
             #[cfg(any(target_os = "linux", target_os = "macos",
-                      target_os = "netbsd"))]
+                      target_os = "netbsd", target_os = "android"))]
             ControlMessage::Ipv4PacketInfo(_) => libc::IPPROTO_IP,
             #[cfg(any(target_os = "linux", target_os = "macos",
-              target_os = "netbsd", target_os = "freebsd"))]
+              target_os = "netbsd", target_os = "freebsd",
+              target_os = "android"))]
             ControlMessage::Ipv6PacketInfo(_) => libc::IPPROTO_IPV6,
         }
     }
@@ -919,10 +924,11 @@ impl<'a> ControlMessage<'a> {
                 libc::UDP_SEGMENT
             },
             #[cfg(any(target_os = "linux", target_os = "macos",
-                      target_os = "netbsd"))]
+                      target_os = "netbsd", target_os = "android"))]
             ControlMessage::Ipv4PacketInfo(_) => libc::IP_PKTINFO,
             #[cfg(any(target_os = "linux", target_os = "macos",
-                      target_os = "netbsd", target_os = "freebsd"))]
+                      target_os = "netbsd", target_os = "freebsd",
+                      target_os = "android"))]
             ControlMessage::Ipv6PacketInfo(_) => libc::IPV6_PKTINFO,
         }
     }