Consider using fftw module from runtime

GNOME runtime version 49 (based on the Freedesktop runtime version 25.08) provides the **fftw** 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 file:**

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

**Some other modules provided by the Freedesktop 25.08**

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

Start by reviewing open pull request #76, then compare the project's build configuration with the Freedesktop SDK 25.08 fftw.bst and platform.bst manifests linked in the issue. Done means determining whether the runtime's fftw module can replace the separately built module and documenting or implementing that decision.

Written by the indexing model from the issue text.