Enable preadv2 optimization on android

Signed-off-by: Jiahao XU <[email protected]>

Author: NobodyXu

src/unix.rs

@@ -290,7 +290,7 @@ impl Client {
         //
         // TODO: musl libc supports preadv2 since 1.2.5, but `libc` crate
         // hasn't yet added it.
-        #[cfg(target_os = "linux")]
+        #[cfg(any(target_os = "linux", target_os = "android"))]
         {
             let read = self.read().as_raw_fd();
             loop {
@@ -397,7 +397,7 @@ impl Client {
 
 // This should be available for all linux targets,
 // though only [`non_blocking_read`] currently uses it so adding gnu cfg.
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "android"))]
 mod linux {
     use super::*;