ocamlbuild should pass -package(...) flags to ocamlfind when building
a -pack-ed file, see

  ocaml/opam-repository#11628 (comment)

Binaries in <bench/*>, <tests/*> depend on the runtime libraries
within ppx_sexp_conv and ocplib-endian.

The packed modules <src/nocrypto.cm{x,o}> also depend on the package
ppx_sexp_conv: its presence at pack-creation time influences the
generated .cmi interface, see

  ocaml/opam-repository#11628 (comment)

Note: the package ppx_sexp_conv.runtime-lib would suffice, but it is
only available as such under recent ppx_sexp_conv versions, so its
explicit use would make the build description (needlessly)
incompatible with older ppx_sexp_conv versions.