guile@2: use `libffi` from macOS.
guile@2: use `libffi` from macOS.

This is the same change as #108775.

Also, depend on `libxcrypt` on Linux.

Closes #108899.

Signed-off-by: BrewTestBot <8a898ee6867e4f2028e63d2a6319b2224641c06c@users.noreply.github.com>

Homebrew/homebrew-core,stgraber/homebrew-core,nandub/homebrew-core,lemzwerg/homebrew-core,sjackman/homebrew-core,sjackman/homebrew-core,lemzwerg/homebrew-core,chrisfinazzo/homebrew-core,filcab/homebrew-core,filcab/homebrew-core,Homebrew/homebrew-core,makigumo/homebrew-core,adam-moss/homebrew-core,chrisfinazzo/homebrew-core,stgraber/homebrew-core,adam-moss/homebrew-core,makigumo/homebrew-core,nandub/homebrew-core