Arm32v7 samples do not build. #3962

Replication:

git clone https://github.com/dotnet/dotnet-docker.git
cd dotnet-docker\samples\dotnetapp
docker build --platform linux/arm/v7 -t dotnetapp .

Error:

`=> ERROR [build 4/6] RUN dotnet restore 0.5s
=> [stage-1 2/3] WORKDIR /app 0.0s

[build 4/6] RUN dotnet restore:
#11 0.466 A fatal error occurred, the folder [/usr/share/dotnet/host/fxr] does not contain any version-numbered child folders
------`

I ran into this which my own working images that I was trying to get running on a RaspberryPI.

All of the online help for that error says my dotnet installation is broken but I am using the MS supply docker so something is really messed up.