Cross compile Docker image targets

Dockerfile

@@ -1,14 +1,28 @@
 # syntax=docker/dockerfile:1
 
-FROM golang:1.24-bookworm AS build
+ARG BUILDPLATFORM
+FROM --platform=$BUILDPLATFORM golang:1.24-bookworm AS build
 
 WORKDIR /src
 
+ARG TARGETARCH
+
+RUN apt-get update \
+  && apt-get install -y --no-install-recommends gcc-aarch64-linux-gnu libc6-dev-arm64-cross \
+  && rm -rf /var/lib/apt/lists/*
+
 COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
-RUN CGO_ENABLED=1 GOOS=linux go build -o /out/archi-folio ./cmd/server
+RUN targetarch="${TARGETARCH:-amd64}" \
+  && echo "building for TARGETARCH=${targetarch}" \
+  && case "$targetarch" in \
+    amd64) export CC=gcc ;; \
+    arm64) export CC=aarch64-linux-gnu-gcc ;; \
+    *) echo "unsupported TARGETARCH=${targetarch}" >&2; exit 1 ;; \
+  esac \
+  && CGO_ENABLED=1 GOOS=linux GOARCH="$targetarch" go build -o /out/archi-folio ./cmd/server
 
 FROM gcr.io/distroless/cc-debian12:nonroot