ProjectSystemProjectOptionsProcessor does not set CompilationOptions when given empty command line

https://github.com/dotnet/roslyn/blob/c5fab36af117b83adfae7a3f4649df415e9de4fb/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LoadedProject.cs#L143

It is expected that after SetCommandLine is called, the associated ProjectSystemProject is updated with non-null CompilationOptions (if it doesn't have the appropriate options on it already).

This doesn't happen when the command line we pass in is `[]`. That's because the constructor calls `ReparseCommandLineIfChanged_NoLock(arguments: []);`, which skips setting CompilationOptions, and when the new call comes in, it is perceived that nothing is changed and there's no need to update.