Using conan in Bazel for linux but not for windows - bazel

Question

I have a system that is built using Bazel and is using OpenCV as a 3rd party package.
When building on Linux I want to use a prebuilt package using conan, and when using Windows I want to use a locally compiled version, and not use conan.
What I have at the moment is in my WORKSPACE file:
load("#//conan:dependencies.bzl", "load_conan_dependencies")
load_conan_dependencies()
new_local_repository(
name = "windows_opencv",
build_file = "#//third_party:opencv_windows.BUILD",
path = "C:\\opencv\\build",
)
and the conanfile.txt looks like this:
[requires]
OpenCV/3.4.13#company/dev
[generators]
BazelDeps
BazelToolchain
This works well for the Linux part, but because I don't have the OpenCV/3.4.13#company/dev package for Windows, I can't use conan install and not rules are generated, so trying to build on Windows causes this error:
ERROR: error loading package '': Label '//conan:dependencies.bzl' is invalid because 'conan' is not a package; perhaps you meant to put the colon here: '//:conan/dependencies.bzl'?
The way I currently see this is I have 2 options:
Have 2 conanfile.txt, 1 which contains the OpenCV package and another empty only with the generators, to create the necessary conan files so it would pass the load call
Create an empty OpenCV conan package and again just insall it so the load call would pass
Both options seems to me like bad hacks and workarounds, but I'm not familiar enough with Bazel to know if there's a better option.
What I would like to be able to do is only load the conan dependencies rule for Linux and ignore it on Windows.
Currently the selection between Linux & Windows OpenCV is done using alias:
alias(
name = "opencv_binary",
actual = select({
"//mediapipe:windows": "#windows_opencv//:opencv",
"//conditions:default": "#opencv//:opencv",
}),
)
where #opencv//:opencv is the conan pacakge