ci(publish): build dashboard-api for arm64 too

GitOrigin-RevId: 5c565710330aa627465e4e7fc727c40d8104b720

Author: svalleru

packages/dashboard-api/Dockerfile

@@ -1,7 +1,10 @@
 ARG GOLANG_VERSION=1.26.8
 ARG ALPINE_VERSION=3.24
 
-FROM golang:${GOLANG_VERSION}-alpine${ALPINE_VERSION} AS builder
+# The builder runs on the build platform and cross-compiles for the target
+# (TARGETARCH -> GOARCH), so an arm64 image is not a QEMU-emulated Go build.
+FROM --platform=$BUILDPLATFORM golang:${GOLANG_VERSION}-alpine${ALPINE_VERSION} AS builder
+ARG TARGETARCH
 
 RUN apk add --no-cache make
 
@@ -45,7 +48,7 @@ WORKDIR /build/dashboard-api
 ARG COMMIT_SHA
 ARG VERSION
 ARG EXPECTED_MIGRATION_TIMESTAMP
-RUN --mount=type=cache,target=/root/.cache/go-build make build COMMIT_SHA=${COMMIT_SHA} VERSION=${VERSION} EXPECTED_MIGRATION_TIMESTAMP=${EXPECTED_MIGRATION_TIMESTAMP}
+RUN --mount=type=cache,target=/root/.cache/go-build GOARCH=${TARGETARCH} make build COMMIT_SHA=${COMMIT_SHA} VERSION=${VERSION} EXPECTED_MIGRATION_TIMESTAMP=${EXPECTED_MIGRATION_TIMESTAMP}
 RUN chmod +x /build/dashboard-api/bin/dashboard-api
 
 FROM alpine:${ALPINE_VERSION}