adding drone config

ci/Dockerfile.sid

@@ -0,0 +1,7 @@
+FROM registry.sean.farm/sid-builder as stage
+COPY . .
+RUN /usr/bin/make -j 8
+
+FROM scratch AS export
+COPY --from=stage /zerotier-one .
+COPY --from=stage /zerotier-cli .

ci/scripts/build.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+set -euo pipefail
+IFS=$'\n\t'
+
+export GOOS=$1
+export GOARCH=$2
+export VERSION=$3
+export DOCKER_BUILDKIT=1
+
+echo "nproc: $(nproc)"
+
+case $GOARCH in
+    armv5)
+        export ARCH=arm/v5
+        ;;
+    armv7)
+        export ARCH=arm/v7
+        ;;
+    arm64)
+        export ARCH=arm64/v8
+        ;;
+    *)
+        export ARCH=$GOARCH
+        ;;
+esac
+
+docker run --privileged --rm tonistiigi/binfmt --install all
+docker buildx build --platform ${GOOS}/${ARCH} -f ci/Dockerfile.sid --target export -t test . --output out/${GOOS}/${GOARCH}