common/syncfs: fall back to sync(2) if syncfs(2) not available

Fixes: #12512
Signed-off-by: Kefu Chai <kchai@redhat.com>
(cherry picked from commit 08210d6)

Conflicts:
	src/common/sync_filesystem.h
          - master does not have #ifdef BTRFS_IOC_SYNC
          - firefly does not have else return -errno clauses in #ifdef HAVE_SYS_SYNCFS

src/common/sync_filesystem.h

@@ -47,6 +47,14 @@ inline int sync_filesystem(int fd)
     return 0;
 #endif
 
+#if defined(HAVE_SYS_SYNCFS) || defined(SYS_syncfs) || defined(__NR_syncfs)
+  else if (errno == ENOSYS) {
+    sync();
+    return 0;
+  } else {
+    return -errno;
+  }
+#else
   sync();
   return 0;
 }