Update openharmony-build.yml

Author: CeSun

.github/workflows/openharmony-build.yml

@@ -49,6 +49,14 @@ jobs:
         with:
           name: packages
           path: output
+      - uses: nuget/setup-nuget@v2
+      - name: Install Mono
+        run: |
+          sudo apt update & sudo apt install dirmngr gnupg apt-transport-https ca-certificates software-properties-common -y
+          sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+          sudo apt-add-repository 'deb https://download.mono-project.com/repo/ubuntu stable-bionic main'
+          sudo apt install mono-complete
+          mono --version
       - name: Push to NuGet
         run: |
           dotnet nuget push **/*.nupkg --api-key ${{ secrets.NUGET_API_KEY }} --source https://api.nuget.org/v3/index.json --skip-duplicate