Auto merge of #3060 - shikhapanwar:sycfs_for_android, r=JohnTitor

ANDROID: Add syncfs API in liblibc

This is required to sync everything in a single filesystem. Other solutions like sync() flushes all filesystems which is unnecessary, it is also impractical to call fsync on all files of the filesystem.

Author: bors

libc-test/semver/android.txt

@@ -3530,6 +3530,7 @@ swapoff
 swapon
 symlink
 symlinkat
+syncfs
 syscall
 sysconf
 sysinfo

src/unix/linux_like/android/mod.rs

@@ -3510,6 +3510,8 @@ extern "C" {
         longopts: *const option,
         longindex: *mut ::c_int,
     ) -> ::c_int;
+
+    pub fn syncfs(fd: ::c_int) -> ::c_int;
 }
 
 cfg_if! {