infra: Workaround Microsoft.NET.ILLink.Tasks restore failure on Flathub

This package seems to be required for triming now but isn't restored by default.
This changes the flatpak pusher to publish so we are sure that the package is in the cache.

Signed-off-by: Mary Guillemard <mary@mary.zone>

.github/workflows/flatpak.yml

@@ -49,7 +49,9 @@ jobs:
         run: python -m pip install PyYAML lxml
 
       - name: Restore Nuget packages
-        run: dotnet restore Ryujinx/${{ env.RYUJINX_PROJECT_FILE }}
+        # With .NET 8.0.100, Microsoft.NET.ILLink.Tasks isn't restored by default and only seems to appears when publishing.
+        # So we just publish to grab the dependencies
+        run: dotnet publish -c Release -r linux-x64 Ryujinx/${{ env.RYUJINX_PROJECT_FILE }} --self-contained
 
       - name: Generate nuget_sources.json
         shell: python