fix multi-platform build

Dockerfile

@@ -1,4 +1,9 @@
-FROM mcr.microsoft.com/dotnet/sdk:8.0-alpine as build
+# QEMU crashes when building arm64 container, so we use this pattern to create a multi-platform build:
+# https://devblogs.microsoft.com/dotnet/improving-multiplatform-container-support/
+FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
+
+# implicitly set by docker build
+ARG TARGETARCH
 
 # install nodejs/npm to build cc-implementation
 RUN apk update && apk add --no-cache nodejs npm
@@ -13,11 +18,11 @@ RUN \
     npm install && \
     npm run build
 
-# compile PushTX app
+# compile PushTX app for target architecture (arm64/amd64)
 RUN \
     cd /app/PushTX && \
-    dotnet restore && \
-    dotnet publish -c Release -o out
+    dotnet restore -a $TARGETARCH && \
+    dotnet publish -a $TARGETARCH --no-restore -c Release -o out
 
 # start from aspnet runtime
 FROM mcr.microsoft.com/dotnet/aspnet:8.0-alpine

Makefile

@@ -3,11 +3,6 @@ PKG_VERSION := $(shell yq e ".version" manifest.yaml)
 TS_FILES := $(shell find ./scripts -name \*.ts)
 SOURCES := $(shell find ./src ! -path "*/obj/*" ! -path "*/bin/*" ! -path "*/node_modules/*")
 
-# sha256 hashes can be found in https://github.com/mikefarah/yq/releases/download/v4.40.7/checksums-bsd
-YQ_VERSION := 4.40.7
-YQ_SHA_AMD64 := 4f13ee9303a49f7e8f61e7d9c87402e07cc920ae8dfaaa8c10d7ea1b8f9f48ed
-YQ_SHA_ARM64 := a84f2c8f105b70cd348c3bf14048aeb1665c2e7314cbe9aaff15479f268b8412
-
 .DELETE_ON_ERROR:
 
 all: verify
@@ -46,9 +41,6 @@ ifeq ($(ARCH),x86_64)
 else
 	mkdir -p docker-images
 	docker buildx build --tag start9/$(PKG_ID)/main:$(PKG_VERSION) \
-		--build-arg PLATFORM=arm64 \
-		--build-arg YQ_VERSION=$(YQ_VERSION) \
-		--build-arg YQ_SHA=$(YQ_SHA_ARM64) \
 		--platform=linux/arm64 -o type=docker,dest=docker-images/aarch64.tar .
 endif
 
@@ -57,9 +49,6 @@ ifeq ($(ARCH),aarch64)
 else
 	mkdir -p docker-images
 	docker buildx build --tag start9/$(PKG_ID)/main:$(PKG_VERSION) \
-		--build-arg PLATFORM=amd64 \
-		--build-arg YQ_VERSION=$(YQ_VERSION) \
-		--build-arg YQ_SHA=$(YQ_SHA_AMD64) \
 		--platform=linux/amd64 -o type=docker,dest=docker-images/x86_64.tar .
 endif