Docker for Windows Containers environment variables - windows

Question

Ok, this seems easy enough for Linux containers but I am trying to get this done using Windows Containers and its annoying that its so difficult.
I have a Windows Dockerfile which builds a project and part of the build process is to reversion the C# AssemblyInfo.cs files so that the built assemblies have a build version from the CI environment (Devops)
I am using a Powershell script https://github.com/microsoft/psi/blob/master/Build/ApplyVersionToAssemblies.ps1, it expects 2 Environment variables, one which I can hardcode so is not a problem, but the BUILD_BUILDNUMBER environment variable needs to be injected from Devops build system.
I have tried the following, none of which work
ARG BUILD_BUILDNUMBER
ENV BUILD_BUILDNUMBER=$BUILD_BUILDNUMBER
RUN ApplyVersionToAssemblies.ps1
and running
docker build -f Dockerfile --build-arg BUILD_BUILDNUMBER=1.2.3.4 .
also
RUN SETX BUILD_BUILDNUMBER $BUILD_BUILDNUMBER
RUN SETX BUILD_BUILDNUMBER %BUILD_BUILDNUMBER%
and a few other combinations that I dont recall, what I ended up doing which works but seems like a hack is to pass the BUILDNUMBER as a file via a COPY and then modifying the the Powershell script to read that into its local variable
So for the moment it works but I would really like to know how this is supposed to work via ARG and ENV for Windows Container builds
Windows Containers definitely feel like Linux containers poor cousin :)

Answer 1

Example for CMD in Docker Windows Containers:
ARG FEED_ACCESSTOKEN
ENV VSS_NUGET_EXTERNAL_FEED_ENDPOINTS="{\"endpointCredentials\": [{\"endpoint\":\"https://URL.com/_packaging/Name/nuget/v3/index.json\", \"username\":\"PATForPackages\", \"password\":\"${FEED_ACCESSTOKEN}\"}]}"
SHELL ["cmd", "/S", "/C"]
RUN echo %VSS_NUGET_EXTERNAL_FEED_ENDPOINTS%