Port to GLnxTmpfile

There's lots of mechanically replacing `OtTmpFile` with `GLnxTmpfile`;
the biggest changes are in the commit path.  Symlink commits are now
very clearly separated from regular files.  Symlinks are `OtCleanupUnlinkat`,
and regular files are `GLnxTmpfile`.

The commit codepath separates those as `_ostree_repo_commit_path_final()` and
`_ostree_repo_commit_tmpf_final()`. A nice aspect of all of this is that they
both *consume* the temporary on success. This avoids an extra spurious
`unlink()` call.

One of the biggest bits of code motion is in `commit_loose_regfile_object()`,
which no longer needs to care about symlinks. For the most parth though it's
just removing conditionals.

Update submodule: libglnx

Closes: #958
Approved by: jlebon

src/libostree/ostree-fetcher-curl.c

@@ -99,7 +99,7 @@ struct FetcherRequest {
   OstreeFetcherRequestFlags flags;
   gboolean is_membuf;
   GError *caught_write_error;
-  OtTmpfile tmpf;
+  GLnxTmpfile tmpf;
   GString *output_buf;
 
   CURL *easy;
@@ -270,9 +270,9 @@ ensure_tmpfile (FetcherRequest *req, GError **error)
 {
   if (!req->tmpf.initialized)
     {
-      if (!ot_open_tmpfile_linkable_at (req->fetcher->tmpdir_dfd, ".",
-                                        O_WRONLY | O_CLOEXEC, &req->tmpf,
-                                        error))
+      if (!glnx_open_tmpfile_linkable_at (req->fetcher->tmpdir_dfd, ".",
+                                          O_WRONLY | O_CLOEXEC, &req->tmpf,
+                                          error))
         return FALSE;
     }
   return TRUE;
@@ -390,9 +390,9 @@ check_multi_info (OstreeFetcher *fetcher)
                   glnx_set_error_from_errno (error);
                   g_task_return_error (task, g_steal_pointer (&local_error));
                 }
-              else if (!ot_link_tmpfile_at (&req->tmpf, GLNX_LINK_TMPFILE_REPLACE,
-                                            fetcher->tmpdir_dfd, tmpfile_path,
-                                            error))
+              else if (!glnx_link_tmpfile_at (&req->tmpf, GLNX_LINK_TMPFILE_REPLACE,
+                                              fetcher->tmpdir_dfd, tmpfile_path,
+                                              error))
                 g_task_return_error (task, g_steal_pointer (&local_error));
               else
                 {
@@ -616,7 +616,7 @@ request_unref (FetcherRequest *req)
   g_ptr_array_unref (req->mirrorlist);
   g_free (req->filename);
   g_clear_error (&req->caught_write_error);
-  ot_tmpfile_clear (&req->tmpf);
+  glnx_tmpfile_clear (&req->tmpf);
   if (req->output_buf)
     g_string_free (req->output_buf, TRUE);
   curl_easy_cleanup (req->easy);