doc: add a release note about proper `sourceRoot` usage

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nixos/doc/manual/release-notes/rl-2311.section.md
··· 162 163 ## Nixpkgs internals {#sec-release-23.11-nixpkgs-internals} 164 165 - The `qemu-vm.nix` module by default now identifies block devices via 166 persistent names available in `/dev/disk/by-*`. Because the rootDevice is 167 identfied by its filesystem label, it needs to be formatted before the VM is
··· 162 163 ## Nixpkgs internals {#sec-release-23.11-nixpkgs-internals} 164 165 + - The use of `sourceRoot = "source";`, `sourceRoot = "source/subdir";`, and similar lines in package derivations using the default `unpackPhase` is deprecated as it requires `unpackPhase` to always produce a directory named "source". Use `sourceRoot = src.name`, `sourceRoot = "${src.name}/subdir";`, or `setSourceRoot = "sourceRoot=$(echo */subdir)";` or similar instead. 166 + 167 - The `qemu-vm.nix` module by default now identifies block devices via 168 persistent names available in `/dev/disk/by-*`. Because the rootDevice is 169 identfied by its filesystem label, it needs to be formatted before the VM is