proof of concept static linked offline_sem

[agle]

Uses promotion of source files to avoid building asli and depending on z3.

building process:

1, in a regular switch dune build @offline && dune promote to generate lifter files
2. Create a fresh switch with static linking opam switch create 5.3.0static 5.3.0+options ocaml-option-musl ocaml-option-static
3. Install zarith static linked to libgmp and mpfr-4.2.2:

• compile libgmp using musl-gcc from source following these instructions Opam install fails with OCaml 4.12 flambda musl static nberth/mlgmpidl#11 (comment)
• install zarith gmp.h not found when compiling with 4.11.1+musl+static+flambda ocaml/Zarith#77 (comment)

4. Build static binary dune build bin/offline_coverage.exe --ignore-promoted-rules

Tested on Debian 6.10.11-1

@katrinafyi