core: Drain fdatasync() API into libgsystem

Just code cleanup.

src/libotutil/ot-unix-utils.c

@@ -190,26 +190,6 @@ ot_util_fatal_gerror (GError *error)
   ot_util_fatal_literal (error->message);
 }
 
-/**
- * ot_unix_fdatasync:
- *
- * Like fdatasync(), but uses #GError, and handles EINTR.
- */
-gboolean
-ot_unix_fdatasync (int fd, GError **error)
-{
-  int result;
-  do
-    result = fdatasync (fd);
-  while (G_UNLIKELY (result != 0 && errno == EINTR));
-  if (result != 0)
-    {
-      ot_util_set_error_from_errno (error, errno);
-      return FALSE;
-    }
-  return TRUE;
-}
-
 /**
  * ot_unix_close:
  *

src/libotutil/ot-unix-utils.h

@@ -55,8 +55,6 @@ gboolean ot_unix_open (const char *path,
                        int        *out_fd,
                        GError    **error);
 
-gboolean ot_unix_fdatasync (int fd, GError **error);
-
 gboolean ot_unix_close (int fd, GError **error);
 
 gboolean ot_unix_open_noatime (const char *path, int *out_fd, GError **error);