Maybe make cross-compiling work?

Dockerfile

@@ -4,7 +4,7 @@
 # base installs required dependencies and runs go mod download to cache dependencies
 #
 FROM --platform=${BUILDPLATFORM} docker.io/golang:1.19-alpine AS base
-RUN apk --update --no-cache add bash build-base
+RUN apk --update --no-cache add bash build-base curl
 
 #
 # build creates all needed binaries
@@ -14,9 +14,11 @@ WORKDIR /src
 ARG TARGETOS
 ARG TARGETARCH
 ARG FLAGS
+ENV GOOS $TARGETOS
+ENV GOARCH $TARGETARCH
 RUN --mount=target=. \
     --mount=type=cache,target=/root/.cache/go-build \
-    GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="${FLAGS}" -trimpath -o /out/ ./cmd/...
+    sh ./build/docker/crossbuild.sh
 
 #
 # The dendrite base image; mainly creates a user and switches to it

build/docker/crossbuild.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+set -ex
+
+case $GOARCH in
+  arm64)
+    curl -s https://musl.cc/aarch64-linux-musl-cross.tgz | tar xz --strip-components=1 -C /usr
+    export CC=aarch64-linux-musl-gcc
+    ;;
+
+  amd64)
+    curl -s https://musl.cc/x86_64-linux-musl-cross.tgz | tar xz --strip-components=1 -C /usr
+    export CC=x86_64-linux-musl-gcc
+    ;;
+
+  i386)
+    curl -s https://musl.cc/i686-linux-musl-cross.tgz | tar xz --strip-components=1 -C /usr
+    export CC=i686-linux-musl-gcc
+    ;;
+
+  arm)
+    curl -s https://musl.cc/armv7l-linux-musleabihf-cross.tgz | tar xz --strip-components=1 -C /usr
+    export CC=armv7l-linux-musleabihf-gcc
+    ;;
+
+  *)
+    echo "Unknown GOARCH=${GOARCH}"
+    exit 1
+    ;;
+esac
+
+go env
+CGO_ENABLED=1 go build -v -ldflags="-linkmode external -extldflags -static ${FLAGS}" -trimpath -o /out/ ./cmd/...