Fix #2816: Update build-ilspy.yml

.github/workflows/build-ilspy.yml

@@ -37,7 +37,7 @@ jobs:
       shell: pwsh
       run: |
         .\BuildTools\ghactions-install.ps1
-        Get-ChildItem Env: | Where-Object {$_.Name -Match "^ILSPY_"} | %{ echo "::set-output name=$($_.Name)::$($_.Value)" }
+        Get-ChildItem Env: | Where-Object {$_.Name -Match "^ILSPY_"} | %{ echo "$($_.Name)=$($_.Value)" } | Out-File -FilePath $Env:GITHUB_OUTPUT -Encoding utf8 -Append
 
     - name: Restore the application
       run: msbuild ILSpy.sln /t:Restore /p:Configuration=${{ matrix.configuration }} /p:Platform=$env:BuildPlatform