feat: updated dockerfile resolving issues on docker build for AMD

Author: jhbritton-RSK

Rsk.Samples.IdentityServer.AdminUiIntegration/Dockerfile

@@ -1,5 +1,7 @@
 # Stage 1 - Build
-FROM --platform=$TARGETPLATFORM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
+FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
+ARG TARGETARCH
+
 WORKDIR /app
 
 # packages installed
@@ -8,24 +10,24 @@ RUN apk update && \
 
 # Copy csproj and restore as distinct layers
 COPY *.csproj .
-RUN dotnet restore
+RUN dotnet restore -a $TARGETARCH
 
 # Copy everything else and build
 COPY . .
-RUN dotnet publish -c Release -o out
+RUN dotnet publish -a $TARGETARCH -o out
 
 # Stage 2 - Runtime
-FROM --platform=$TARGETPLATFORM mcr.microsoft.com/dotnet/aspnet:8.0-alpine AS runtime
+FROM mcr.microsoft.com/dotnet/aspnet:8.0-alpine AS runtime
 
 # Ensuring latest openssl is installed as the one in base
 # is out of date and vulnerable
 RUN apk update && \
     apk upgrade && \
     apk upgrade openssl
 
-ENV ASPNETCORE_ENVIRONMENT Production
+ENV ASPNETCORE_ENVIRONMENT=Production
 ENV ASPNETCORE_HTTP_PORT=5003
-ENV ASPNETCORE_URLS http://*:5003
+ENV ASPNETCORE_URLS=http://*:5003
 ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=false
 
 EXPOSE 5003