How to use mingw-w64 to cross compile a plugin from linux dev environment to windows for running?

Question

I've been having a great time with my gdnative c++ godot plugin, but the time has come to try to run the plugin on a different operating system. I know that in the documentation under https://docs.godotengine.org/en/stable/development/compiling/compiling_for_windows.html#cross-compiling-for-windows-from-other-operating-systems they suggest using mingw-w64 and I have managed to compile the godot-cpp with that, but when I modify the SConstruct file from here https://docs.godotengine.org/en/stable/_downloads/988fdf9bf1fed6991e760aadf423d3df/SConstruct and make some modifications (see under section starting with elif env['platform'] == "windows" and host_platform =="linux":) after I run sconstruct platform=windows target=release I get an .so file in the path that I expected a .dll

#!python
import os
import sys
opts = Variables([], ARGUMENTS)
if sys.platform.startswith("linux"):
    host_platform = "linux"
elif sys.platform.startswith("freebsd"):
    host_platform = "freebsd"
elif sys.platform == "darwin":
    host_platform = "osx"
elif sys.platform == "win32" or sys.platform == "msys":
    host_platform = "windows"
else:
    raise ValueError("Could not detect platform automatically, please specify with platform=<platform>")

# Gets the standard flags CC, CCX, etc.
env = DefaultEnvironment()

# Define our options
opts.Add(EnumVariable('target', "Compilation target", 'debug', ['d', 'debug', 'r', 'release']))
opts.Add(EnumVariable('platform', "Compilation platform", '', ['', 'windows', 'x11', 'linux', 'osx']))
opts.Add(EnumVariable('p', "Compilation target, alias for 'platform'", '', ['', 'windows', 'x11', 'linux', 'osx']))
opts.Add(BoolVariable('use_llvm', "Use the LLVM / Clang compiler", 'no'))
opts.Add(PathVariable('target_path', 'The path where the lib is installed.', 'demo/bin/'))
opts.Add(PathVariable('target_name', 'The library name.', 'libgdexample', PathVariable.PathAccept))

# Local dependency paths, adapt them to your setup
godot_headers_path = "godot-cpp/godot-headers/"
cpp_bindings_path = "godot-cpp/"
cpp_library = "libgodot-cpp"

# only support 64 at this time..
bits = 64

# Updates the environment with the option variables.
opts.Update(env)

# Process some arguments
if env['use_llvm']:
    env['CC'] = 'clang'
    env['CXX'] = 'clang++'

if env['p'] != '':
    env['platform'] = env['p']

if env['platform'] == '':
    print("No valid target platform selected.")
    quit();

# For the reference:
# - CCFLAGS are compilation flags shared between C and C++
# - CFLAGS are for C-specific compilation flags
# - CXXFLAGS are for C++-specific compilation flags
# - CPPFLAGS are for pre-processor flags
# - CPPDEFINES are for pre-processor defines
# - LINKFLAGS are for linking flags

# Check our platform specifics
if env['platform'] == "osx":
    env['target_path'] += 'osx/'
    cpp_library += '.osx'
    env.Append(CCFLAGS=['-arch', 'x86_64'])
    env.Append(CXXFLAGS=['-std=c++17'])
    env.Append(LINKFLAGS=['-arch', 'x86_64'])
    if env['target'] in ('debug', 'd'):
        env.Append(CCFLAGS=['-g', '-O2'])
    else:
        env.Append(CCFLAGS=['-g', '-O3'])

elif env['platform'] in ('x11', 'linux'):
    env['target_path'] += 'x11/'
    cpp_library += '.linux'
    env.Append(CCFLAGS=['-fPIC'])
    env.Append(CXXFLAGS=['-std=c++17'])
    if env['target'] in ('debug', 'd'):
        env.Append(CCFLAGS=['-g3', '-Og'])
    else:
        env.Append(CCFLAGS=['-g', '-O3'])

elif env['platform'] == "windows" and host_platform =="windows":
    env['target_path'] += 'win64/'
    cpp_library += '.windows'
    # This makes sure to keep the session environment variables on windows,
    # that way you can run scons in a vs 2017 prompt and it will find all the required tools
    env.Append(ENV=os.environ)

    env.Append(CPPDEFINES=['WIN32', '_WIN32', '_WINDOWS', '_CRT_SECURE_NO_WARNINGS'])
    env.Append(CCFLAGS=['-W3', '-GR'])
    env.Append(CXXFLAGS='/std:c++17')
    if env['target'] in ('debug', 'd'):
        env.Append(CPPDEFINES=['_DEBUG'])
        env.Append(CCFLAGS=['-EHsc', '-MDd', '-ZI'])
        env.Append(LINKFLAGS=['-DEBUG'])
    else:
        env.Append(CPPDEFINES=['NDEBUG'])
        env.Append(CCFLAGS=['-O2', '-EHsc', '-MD'])
elif env['platform'] == "windows" and host_platform =="linux":
    env['target_path'] += 'win64/'
    cpp_library += '.windows'
    # This makes sure to keep the session environment variables on windows,
    # that way you can run scons in a vs 2017 prompt and it will find all the required tools
    env["CXX"] = "x86_64-w64-mingw32-g++"
    env["AR"] = "x86_64-w64-mingw32-ar"
    env["RANLIB"] = "x86_64-w64-mingw32-ranlib"
    env["LINK"] = "x86_64-w64-mingw32-g++"

    env.Append(CCFLAGS=["-O3", "-Wwrite-strings"])
    env.Append(
        LINKFLAGS=[
            "--static",
            "-Wl,--no-undefined",
            "-static-libgcc",
            "-static-libstdc++",
        ]
    )
    # env.Append(ENV=os.environ)

    # env.Append(CPPDEFINES=['WIN32', '_WIN32', '_WINDOWS', '_CRT_SECURE_NO_WARNINGS'])
    # env.Append(CCFLAGS=['-W3', '-GR'])
    # env.Append(CCFLAGS=['-W3', '-GR'])
    # env.Append(CXXFLAGS='/std:c++17')
    # if env['target'] in ('debug', 'd'):
    #     env.Append(CPPDEFINES=['_DEBUG'])
    #     env.Append(CCFLAGS=['-EHsc', '-MDd', '-ZI'])
    #     env.Append(LINKFLAGS=['-DEBUG'])
    # else:
    #     env.Append(CPPDEFINES=['NDEBUG'])
    #     env.Append(CCFLAGS=['-O2', '-EHsc', '-MD'])

if env['target'] in ('debug', 'd'):
    cpp_library += '.debug'
else:
    cpp_library += '.release'

cpp_library += '.' + str(bits)

# make sure our binding library is properly includes
env.Append(CPPPATH=['.', godot_headers_path, cpp_bindings_path + 'include/', cpp_bindings_path + 'include/core/', cpp_bindings_path + 'include/gen/'])
env.Append(LIBPATH=[cpp_bindings_path + 'bin/'])
env.Append(LIBS=[cpp_library])

# tweak this if you want to use different folders, or more folders, to store your source code in.
env.Append(CPPPATH=['src/'])
sources = Glob('src/*.cpp')

print("debugging output name",env["target_name"],cpp_library)
library = env.SharedLibrary(target=env['target_path'] + env['target_name'] , source=sources)

Default(library)

# Generates help for the -h scons option.
Help(opts.GenerateHelpText(env))

output of scons command shown here

gitpod /workspace/phytoVRgodot (main) $ scons platform=windows target=release 
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
x86_64-w64-mingw32-g++ -o src/gdexample.os -c -O3 -Wwrite-strings -fPIC -I. -Igodot-cpp/godot-headers -Igodot-cpp/include -Igodot-cpp/include/core -Igodot-cpp/include/gen -Isrc src/gdexample.cpp
x86_64-w64-mingw32-g++ -o src/gdlibrary.os -c -O3 -Wwrite-strings -fPIC -I. -Igodot-cpp/godot-headers -Igodot-cpp/include -Igodot-cpp/include/core -Igodot-cpp/include/gen -Isrc src/gdlibrary.cpp
x86_64-w64-mingw32-g++ -o demo/bin/win64/libgdexample.so --static -Wl,--no-undefined -static-libgcc -static-libstdc++ -shared src/gdexample.os src/gdlibrary.os -Lgodot-cpp/bin -lgodot-cpp.windows.release.64
scons: done building targets.

So the question is, how can I construct an SConstruct file so that it produces a .dll compiled on linux with mingw-w64 that I can use to load my custom plugin as gdnative script in windows?