fix android build

Author: devnexen

library/std/src/os/net/linux_ext/tcp.rs

@@ -76,6 +76,7 @@ pub trait TcpStreamExt: Sealed {
     /// stream.set_deferaccept(1).expect("set_deferaccept call failed");
     /// ```
     #[unstable(feature = "tcp_deferaccept", issue = "119639")]
+    #[cfg(target_os = "linux")]
     fn set_deferaccept(&self, accept: u32) -> io::Result<()>;
 
     /// Gets the accept delay value (in seconds) of the `TCP_DEFER_ACCEPT` option.
@@ -95,6 +96,7 @@ pub trait TcpStreamExt: Sealed {
     /// assert_eq!(stream.deferaccept().unwrap_or(0), 1);
     /// ```
     #[unstable(feature = "tcp_deferaccept", issue = "119639")]
+    #[cfg(target_os = "linux")]
     fn deferaccept(&self) -> io::Result<u32>;
 }
 
@@ -111,10 +113,12 @@ impl TcpStreamExt for net::TcpStream {
         self.as_inner().as_inner().quickack()
     }
 
+    #[cfg(target_os = "linux")]
     fn set_deferaccept(&self, accept: u32) -> io::Result<()> {
         self.as_inner().as_inner().set_deferaccept(accept)
     }
 
+    #[cfg(target_os = "linux")]
     fn deferaccept(&self) -> io::Result<u32> {
         self.as_inner().as_inner().deferaccept()
     }