dockerfile: Add multi-arch image build

Dockerfile

@@ -8,7 +8,6 @@ WORKDIR /headlamp-plugins
 # Add multi-arch build arguments
 ARG PLUGIN
 ARG TARGETPLATFORM
-ARG TARGETOS
 ARG TARGETARCH
 
 # Check if the PLUGIN argument is provided
@@ -17,6 +16,12 @@ RUN if [ -z "$PLUGIN" ]; then \
       exit 1; \
     fi
 
+# Enforce that TARGETARCH is specified
+RUN if [ -z "$TARGETARCH" ]; then \
+      echo "Error: TARGETARCH argument is required"; \
+      exit 1; \
+    fi
+
 # Create a directory for the plugin build
 RUN mkdir -p /headlamp-plugins/build/${PLUGIN}
 
@@ -48,4 +53,4 @@ LABEL org.opencontainers.image.licenses=MIT
 LABEL org.opencontainers.image.platform=$TARGETPLATFORM
 
 # Set the default command to list the installed plugins
-CMD ["sh", "-c", "echo Plugins installed at /plugins/:; ls /plugins/"]
+CMD ["sh", "-c", "echo Plugins installed at /plugins/:; ls /plugins/"]