qemu 8.1.0 rc tarballs are broken, missing subproject content
Description of problem:
The released tarballs for 8.1.0 rc releases (both rc0 adn rc1) are missing the
subproject content. Only the submodule content appears present
Steps to reproduce:
1. `wget http://download.qemu.org/qemu-8.1.0-rc1.tar.xz`
2. `tar Jxvf qemu-8.1.0-rc1.tar.xz`
3. `cd qemu-8.1.0-rc1`
4. `./configure  --target-list=x86_64-softmmu --disable-download`

```
Using './build' as the directory for build output

ERROR: missing subprojects

This is not a GIT checkout but subproject content appears to
be missing. Do not use 'git archive' or GitHub download links
to acquire QEMU source archives. Non-GIT builds are only
supported with source archives linked from:

  https://www.qemu.org/download/#source

Developers working with GIT can use scripts/archive-source.sh
if they need to create valid source archives.

```

The missing subprojects are

```
 berkeley-softfloat-3
 berkeley-testfloat-3
 dtc
 keycodemapdb
 libvfio-user
```

If I use 'make-release . 8.1.0-rc1' to create a tarball from git, it has all the expected content.

IOW, either the release tarballs are not being created using 'make-release', or there's something broken with 'make-release' in some scenarios