Installing from opam relies on unavailable versions of llvm-config

[ErrWare]

I failed to install bap from opam because it requires very old versions of llvm-config that are unavailable from my institution's repos. Ideally the bap on the opam repos would rely on newer versions of llvm-config.

The versions bap needs are:

llvm-config-90
llvm-config-9
llvm-config-8.0
llvm-config-80
llvm-config-8
llvm-config-7.0
llvm-config-70
llvm-config-7
llvm-config-6.0
llvm-config-60
llvm-config-6