Consider using xxhash module from runtime

GNOME runtime version 49 (based on the Freedesktop runtime version **25.08**) appears to provide the **xxhash** module.

In most cases, you don't need to build this module separately, unless your project requires a specific version or a custom configuration.

**Related manifest files**

https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/blob/release/25.08/elements/bootstrap/xxhash.bst
https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/blob/release/25.08/elements/bootstrap/include/xxhash-source.yml

**Other modules provided by the Freedesktop 25.08**

https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/blob/release/25.08/elements/platform.bst

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This is general information for repositories using xxhash modules. I have no intention of interfering with the developers' work.

Start by locating the repository's Flatpak or Freedesktop manifest and compare its xxhash build entry with the referenced Freedesktop 25.08 elements/bootstrap/xxhash.bst and platform.bst files. Confirm that the GNOME 49 runtime supplies the required module and check whether the project needs a specific version or configuration. Done means the redundant build is removed only if the runtime dependency is sufficient.

Written by the indexing model from the issue text.