requiring "core" in utop gives error: Unix.Unix_error (Unix.ENOENT, "sysconf", "")

Question

When I try to call #require "core" in utop, I get an error:

utop # #require "core";;
Exception: Unix.Unix_error (Unix.ENOENT, "sysconf", "").
Raised by primitive operation at unknown location
Called from file "toplevel/topdirs.ml", line 144, characters 10-51

I have a .ocamlinit file that looks like this in my current directory:

(* Added by OPAM. *)
let () =
  try Topdirs.dir_directory (Sys.getenv "OCAML_TOPLEVEL_PATH")
  with Not_found -> ()
;;

#use "topfind";;
#thread;;
#camlp4o;;

What could be causing this error to happen? It appears to be an error from Findlib?

I tried wiping away my ~/.opam directory, rerunning opam init, opam switch set 4.05.0, and reinstalling core and utop, but this error persists. Is it possible that I also need to reinstall opam itself? I am currently using a binary version of opam-1.2.2.

I'm running Arch Linux, and I believe this error started occuring after updating all the packages on my system, but I am not sure.

I am still able to use jbuilder to build executables, but when running the executables, they fail with a similar error:

$ _build/install/default/bin/my_executable
Uncaught exception:

  (Unix.Unix_error "Illegal seek" sysconf "")

Raised by primitive operation at unknown location

I am pretty sure this is not an exception being cause by my code, but is similar to the error occuring in utop.

I have a jbuild file that looks like this:

(jbuild_version 1)

(executable
 ((name main)
  (libraries (my_library))))

(install
 ((section bin)
  (files ((main.exe as my_executable)))))

---

edit: I've tried using different versions of opam and the compiler, including the system compiler (which is also version 4.05.0). Nothing seems to work. Every combination produces the same errors as above.