MSys2 fails to compile topkg.1.1.0

[jmid]

The msys2 failure (I've no clue what to do about it, it seems unrelated to this PR):

  #=== ERROR while compiling topkg.1.1.0 ========================================#
  # context     2.4.1 | win32/x86_64 | ocaml.5.3.0 | file://D:/a/opam-repository/opam-repository
  # path        D:\opamroot\default\.opam-switch\build\topkg.1.1.0
  # command     D:\opamroot\default\bin\ocaml.exe pkg/pkg.ml build --pkg-name topkg --dev-pkg false
  # exit-code   125
  # env-file    D:\opamroot\log\topkg-1688-3bd6f4.env
  # output-file D:\opamroot\log\topkg-1688-3bd6f4.out
  ### output ###
  # Exception: Fl_package_base.No_such_package ("findlib", "").

Originally posted by @hannesm in #28624 (comment)

I've also spotted this on the MSys2 workflow for #28634