split up offline lifter opam package for smaller size

[katrinafyi]

the aslp_lifter_ocaml package currently includes both the pc and non-pc versions. we could split this up to halve the disk usage and build time.

812K    /home/rina/.opam/ocaml5/lib/aslp_lifter_ocaml/offlineASL_runner
832K    /home/rina/.opam/ocaml5/lib/aslp_lifter_ocaml/offlineASL_pc_runner
396M    /home/rina/.opam/ocaml5/lib/aslp_lifter_ocaml/aarch64
398M    /home/rina/.opam/ocaml5/lib/aslp_lifter_ocaml/pc_aarch64
795M    /home/rina/.opam/ocaml5/lib/aslp_lifter_ocaml/