Fix cross compile (#10952)

* Fix cross compile

* Add test for cross compile

* Fix drone

* Fix drone

* Also prevent CC environment not to generate

Co-authored-by: zeripath <art27@cantab.net>

.drone.yml

@@ -51,6 +51,21 @@ steps:
       - go build -mod=vendor -o gitea_no_gcc # test if build succeeds without the sqlite tag
     depends_on: [lint-backend]
 
+  - name: build-backend-arm64
+    pull: always
+    image: golang:1.14
+    environment:
+      GO111MODULE: on
+      GOPROXY: off
+      GOOS: linux
+      GOARCH: arm64
+      TAGS: bindata
+    commands:
+      - curl -sL https://deb.nodesource.com/setup_12.x | bash - && apt -y install nodejs
+      - make build # test cross compile
+      - rm ./gitea # clean
+    depends_on: [lint-backend]
+
   - name: build-backend-386
     pull: always
     image: golang:1.14