Enable cross platform builds / be more specific about output arch from drone

.drone.yml

@@ -27,11 +27,11 @@ steps:
         path: /drone/src/out
     commands:
       - cd /drone/src
-      - go build -o out/wifi cmd/wifi/wifi.go
-      - go build -o out/inotify cmd/inotify/inotify.go
-      - go build -o out/gui cmd/gui/gui.go
-      - go build -o out/fan cmd/fan/fan.go
-      - go build -o out/hdmi cmd/hdmi/hdmi.go
+      - env GOOS=linux GOARCH=arm64 go build -o out/wifi cmd/wifi/wifi.go
+      - env GOOS=linux GOARCH=arm64 go build -o out/inotify cmd/inotify/inotify.go
+      - env GOOS=linux GOARCH=arm64 go build -o out/gui cmd/gui/gui.go
+      - env GOOS=linux GOARCH=arm64 go build -o out/fan cmd/fan/fan.go
+      - env GOOS=linux GOARCH=arm64 go build -o out/hdmi cmd/hdmi/hdmi.go
       - cp CHANGELOG.md out/
   - name: gitea-release
     image: plugins/gitea-release