soup: Reintroduce compile-time libsoup dependency for static builds

soup: Reintroduce compile-time libsoup dependency for static builds

On Android (especially) and for static builds in general it is safer to link
against libsoup and have the dynamic custom loading disabled. For those cases we
can safely assume the application will use either libsoup2 or libsoup3 and not
both.

Fixes #939

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1536>