support github actions

.github/workflows/build-snapshot.yml

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+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+# Controls when the action will run. 
+on:
+  # Triggers the workflow on push or pull request events but only for the main branch
+  schedule:
+    - cron: '0 3 * * *'
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: self-hosted
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+
+      # build source code
+      - name: build
+        run: cd ~/work/runner-script/sdk4_script && ./build_firmware_by_source
+
+      - uses: actions/upload-artifact@v2
+        with:
+          name: ./snapshot_firmware
+          path: |
+		./bin/target/**/*squashfs-sysupgrade.bin
+		./bin/target/**/*squashfs-sysupgrade.img
+		./bin/target/**/*squashfs-sysupgrade.tar