doc: Mention the flat directory structure for uploads

The uploaded binaries need to match the same flat directory structure of
the SHA256SUMS file in order for torrent downloaders to be able to
verify the download without moving files. Mention this in the release
process doc.

doc/release-process.md

@@ -206,17 +206,26 @@ cat "$VERSION"/*/all.SHA256SUMS.asc > SHA256SUMS.asc
 ```
 
 
-- Upload to the bitcoincore.org server (`/var/www/bin/bitcoin-core-${VERSION}`):
-    1. The contents of `./bitcoin/guix-build-${VERSION}/output`, except for
+- Upload to the bitcoincore.org server (`/var/www/bin/bitcoin-core-${VERSION}/`):
+    1. The contents of each `./bitcoin/guix-build-${VERSION}/output/${HOST}/` directory, except for
        `*-debug*` files.
 
+       Guix will output all of the results into host subdirectories, but the SHA256SUMS
+       file does not include these subdirectories. In order for downloads via torrent
+       to verify without directory structure modification, all of the uploaded files
+       need to be in the same directory as the SHA256SUMS file.
+
        The `*-debug*` files generated by the guix build contain debug symbols
        for troubleshooting by developers. It is assumed that anyone that is
        interested in debugging can run guix to generate the files for
        themselves. To avoid end-user confusion about which file to pick, as well
        as save storage space *do not upload these to the bitcoincore.org server,
        nor put them in the torrent*.
 
+       ```sh
+       find guix-build-${VERSION}/output/ -maxdepth 2 -type f -not -name "SHA256SUMS.part" -and -not -name "*debug*" -exec scp {} [email protected]:/var/www/bin/bitcoin-core-${VERSION} \;
+       ```
+
     2. The `SHA256SUMS` file
 
     3. The `SHA256SUMS.asc` combined signature file you just created