From 0e4c0035b6a64855541f6b4886b9455272d3cba0 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Mon, 3 Oct 2022 17:25:46 +0100
Subject: [PATCH] Maybe make cross-compiling work?

---
 Dockerfile                 |  6 ++++--
 build/docker/crossbuild.sh | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)
 create mode 100644 build/docker/crossbuild.sh

diff --git a/Dockerfile b/Dockerfile
index 10861a95c..2f1686672 100644
--- a/Dockerfile
+++ b/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
diff --git a/build/docker/crossbuild.sh b/build/docker/crossbuild.sh
new file mode 100644
index 000000000..35b2fe85a
--- /dev/null
+++ b/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/...
\ No newline at end of file