Declare O_RSYNC for Android.

Bionic defines it to be `O_SYNC`.

Author: whitequark

src/unix/linux_like/android/mod.rs

@@ -1101,6 +1101,7 @@ pub const O_SYNC: ::c_int = 0x101000;
 pub const O_ASYNC: ::c_int = 0x2000;
 pub const O_NDELAY: ::c_int = 0x800;
 pub const O_DSYNC: ::c_int = 4096;
+pub const O_RSYNC: ::c_int = O_SYNC;
 
 pub const NI_MAXHOST: ::size_t = 1025;
 pub const NI_MAXSERV: ::size_t = 32;