guile-3.0 uses libxcrypt during build, but it also exposes this header
to its downstreams by including -lcrypt in its pkgconf .pc file. There
is an effort[1] to drop libcrypt-dev from the build-essential package
set. This will not happen during the trixie freeze, but some months into
the forky cycle. Once dropped, guile-3.0 and reverse dependencies of
guile-3.0-dev will fail to build from source. I'm attaching a patch to
make these dependencies explicit. It is safe for inclusion into trixie,
but it does not warrant an upload of its own at this time of the freeze.

Helmut

[1] https://lists.debian.org/debian-devel/2025/04/msg00113.html