Cannot resolve symbols for swscanf

Using https://github.com/ocaml/setup-ocaml/pull/794

#=== ERROR while compiling dune.3.15.2 ========================================#
# context     2.2.0~beta2 | win32/x86_64 | ocaml-base-compiler.4.14.2 | git+https://github.com/dra27/opam-repository.git#windows-initial
# path        D:\a\mirage-torrent\mirage-torrent\_opam\.opam-switch\build\dune.3.15.2
# command     D:\a\mirage-torrent\mirage-torrent\_opam\bin\ocaml.exe boot/bootstrap.ml -j 4
# exit-code   2
# env-file    D:\.opam\log\dune-8180-dff03d.env
# output-file D:\.opam\log\dune-8180-dff03d.out
### output ###
# ocamlc -output-complete-exe -w -24 -g -o .duneboot.exe -I boot unix.cma boot/libs.ml boot/duneboot.ml
# ** Cannot resolve symbols for D:/a/mirage-torrent/mirage-torrent/_opam/lib/ocaml\libcamlrun.a(startup_aux.b.o):
#  swscanf
# ** Cannot resolve symbols for descriptor object:
#  _vscwprintf
# File "boot/duneboot.ml", line 1:
# Error: Error while building custom runtime system

Start by reviewing setup-ocaml pull request 794 and the failing Dune bootstrap command in boot/bootstrap.ml on Windows. Investigate how flexdll handles the unresolved swscanf and _vscwprintf symbols, then verify that the Dune custom runtime builds successfully in the reported OCaml and Windows environment.