conf-zmq doesn't install zmq on Windows

[Lysxia]

Using the standard Github Action for OCaml, for a Windows build of a project depending on zmq, the installation of conf-zmq fails:

#=== ERROR while compiling conf-zmq.0.1 =======================================#
# context     2.3.0 | win32/x86_64 | ocaml-base-compiler.5.2.1 | git+https://github.com/ocaml/opam-repository.git
# path        D:\a\creusot-ide\creusot-ide\_opam\.opam-switch\build\conf-zmq.0.1
# command     D:\cygwin\bin\sh.exe -c cc test.c $(pkg-config --libs --cflags libzmq)
# exit-code   127
# env-file    D:\.opam\log\conf-zmq-6188-b0ca09.env
# output-file D:\.opam\log\conf-zmq-6188-b0ca09.out
### output ###
# Package libzmq was not found in the pkg-config search path.
# Perhaps you should add the directory containing `libzmq.pc'
# to the PKG_CONFIG_PATH environment variable
# Package 'libzmq' not found
# /usr/bin/sh: line 1: cc: command not found

It seems the Windows environment for GHA doesn't match {os = "win32" & os-distribution = "cygwinports"} in conf-zmq's opam config.

opam-repository/packages/conf-zmq/conf-zmq.0.1/opam

Line 17 in 1db3104

["zeromq"] {os = "win32" & os-distribution = "cygwinports"}