tree-wide: Update to new libglnx fd APIs

This ends up a lot better IMO.  This commit is *mostly* just
`s/glnx_close_fd/glnx_autofd`, but there's also a number of hunks like:

```
-  if (self->sysroot_fd != -1)
-    {
-      (void) close (self->sysroot_fd);
-      self->sysroot_fd = -1;
-    }
+  glnx_close_fd (&self->sysroot_fd);
```

Update submodule: libglnx

Closes: #1259
Approved by: jlebon

src/rofiles-fuse/main.c

@@ -268,7 +268,7 @@ callback_chown (const char *path, uid_t uid, gid_t gid)
 static int
 callback_truncate (const char *path, off_t size)
 {
-  glnx_fd_close int fd = -1;
+  glnx_autofd int fd = -1;
 
   path = ENSURE_RELPATH (path);
   VERIFY_WRITE(path);