fail to build zarith dependancy in monorepo for hvt target

[RyanGibb]

www-dev> File "duniverse/Zarith/dune", line 24, characters 0-159:
www-dev> 24 | (rule
www-dev> 25 |  (target Makefile)
www-dev> 26 |  (deps configure config.guess env)
www-dev> 27 |  (action
www-dev> 28 |   (bash
www-dev> 29 |    "env %{read:env} ./configure --ocamllibdir %{ocaml-config:standard_library}")))
www-dev> binary ocaml: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> binary ocamlc: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> binary ocamldep: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> binary ocamlmklib: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> binary ocamldoc: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> binary x86_64-solo5-none-static-cc: found in /nix/store/8wq2cpj1pavj1ks771wxj97hxpwg347v-solo5-0.7.3/bin
www-dev> binary ocamlopt: found in /nix/store/28sj9b4cj9z8h11zs002xja7136b21ri-ocaml-4.14.0/bin
www-dev> checking compilation with x86_64-solo5-none-static-cc -I/nix/store/zm57y1mxc52kji4jvg5yc3z7l42zfl9p-ocaml-solo5-0.8.1/solo5-sysroot/include/nolibc/ -include _solo5/overrides.h -O2 -fno-strict-aliasing -fwrapv : working
www-dev> include caml/mlvalues.h: found
www-dev> library dynlink.cmxa: found
www-dev> binary ocamlfind: found in /nix/store/y8v64yx17fkk11y3qj8iry09awhrkp6b-ocamlfind-1.9.5/bin
www-dev> OCaml's word size is 64
www-dev> binary uname: found in /nix/store/n95s7s6ilkjc7xwqml93acxzj6k0hsfn-coreutils-9.1/bin
www-dev> include gmp.h: found
www-dev> library gmp: not found
www-dev> include mpir.h: not found
www-dev> cannot find GMP nor MPIR

[RyanGibb]

zarith/configure doesn't seem to pick up the gmp library. Strangely it does find the header though.

[RyanGibb]

possibilities:

• ./configure does some weird stuff to ignore NIX_LDFLAGS (like not using gcc-wrapper
  • building zarith locally would seem to imply this is not the case as it works when setting NIX_LDFLAGS with a nix shell or manually setting LDFLAGS=-L/nix/store/<hash>-gmp-with-cxx-6.2.1/lib
• dune build is doing some sandboxing preventing gcc-wrapper being used or NIX_LDFLAGS read
  • building zarith locally would seem to imply this is also not the case as it works inside a dune build
• it's a problem with building in a nix derivation for some reason?
  • again building zarith locally works fine in a nix derivation

[RyanGibb]

The fact that this works for unix but not hvt implies it's a cross compilation issue

[RyanGibb]

This seems to be because https://github.com/mirage/ocaml-gmp isn't being picked up in our monorepo. It worked for unix as we used the system dependancy

[RyanGibb]

So Zarith depends on ("gmp" | "conf-gmp" ) which opam admin list in tweag/opam-nix doesn't seem to pick up.

We should look at using opam-monorepo

[RyanGibb]

Manually adding gmp = "*" to the monorepo query results in:

 www-dev> File "duniverse/ocaml-gmp/src/dune", line 25, characters 0-110:
 www-dev> 25 | (rule
 www-dev> 26 |  (targets build.sh)
 www-dev> 27 |  (deps build.sh.in)
 www-dev> 28 |  (mode fallback)
 www-dev> 29 |  (action
 www-dev> 30 |   (run opam config subst "build.sh")))
 www-dev> Error: Rule failed to generate the following targets:
 www-dev> - duniverse/ocaml-gmp/src/build.sh

[RyanGibb]

Fixed by RyanGibb/hillingar@b6e7205