Add release mirror CI job

.github/workflows/Release.yml

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+name: Mirror SDK
+
+on:
+  push:
+    tags:
+     - "v*.*"
+jobs:
+  download:
+    strategy:
+      matrix:
+        artifact_name:
+          - ohos-sdk-windows_linux-public.tar.gz
+          - L2-SDK-MAC-M1-PUBLIC.tar.gz
+          - ohos-sdk-mac-public.tar.gz
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Download OpenHarmony SDK
+        run: ./download_sdk.sh
+        shell: bash
+        env:
+          # Relies on this job only running on tags!
+          INPUT_VERSION_TAG: "${{ github.ref_name }}"
+          INPUT_FILENAME: ${{ matrix.artifact_name}}
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.artifact_name}}
+          path: ${{ matrix.artifact_name}}*
+          compression-level: 0
+
+  create_release:
+    permissions: write-all
+    runs-on: ubuntu-latest
+    needs: ["download"]
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          merge-multiple: true
+      - run: ls -la
+      - name: Publish release
+        id: publish-release
+        run: |
+          artifacts=(./*)
+          gh release create ${{github.ref_name}} --notes "OpenHarmony SDK mirror release for ${{github.ref_name}}" "${artifacts[@]}"

README.md

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+# OpenHarmony SDK mirror
+
+The OpenHarmony SDK is available for download via links in the OpenHarmony release notes.
+However, the speed of these downloads can often be too slow for use in CI environments.
+Hence, this repository provides a mirror of the released OpenHarmony SDKs, allowing quick downloads
+in Github actions.

download_sdk.sh

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+#!/usr/bin/env bash
+
+# Script to download an upstream SDK release
+
+set -eux
+
+: "${INPUT_VERSION_TAG:?INPUT_VERSION_TAG needs to be set}"
+: "${INPUT_FILENAME:?INPUT_FILENAME needs to be set}"
+
+VERSION="${INPUT_VERSION_TAG:1}"
+
+# https://repo.huaweicloud.com/openharmony/os/4.0-Release/ohos-sdk-windows_linux-public.tar.gz
+
+URL_BASE="https://repo.huaweicloud.com/openharmony/os"
+
+DOWNLOAD_URL="${URL_BASE}/${VERSION}-Release/${INPUT_FILENAME}"
+
+echo "Downloading OHOS SDK from ${DOWNLOAD_URL}"
+
+curl --fail -L --remote-name "${DOWNLOAD_URL}"
+curl --fail -L --remote-name "${DOWNLOAD_URL}.sha256"
+
+echo "$(cat "${INPUT_FILENAME}".sha256) ${INPUT_FILENAME}" | sha256sum --check --status