Detect multiple conflicting assemblies being passed to crossgen

[kg]

Should fix #114513

[jkotas]

I think this is too late to detect duplicates.

crossgen, ilc and ilverify are all on first reference wins plan for references and ignore duplicates.

The duplicates are eliminated very early during command line parsing at

runtime/src/coreclr/tools/Common/CommandLineHelpers.cs

Lines 347 to 358 in 0621e64

	if (dictionary.TryGetValue(simpleName, out string otherFullFileName))
	{
	if (strict)
	{
	throw new CommandLineException("Multiple input files matching same simple name " +
	fullFileName + " " + otherFullFileName);
	}
	}
	else
	{
	dictionary.Add(simpleName, fullFileName);
	}

.

strict flag is true for input assemblies and it is false for references.

[jkotas]

Changing the policy for duplicates is likely going to break some of the folks who are invoking crossgen manually. Manual invoked crossgen command line often references using wildcards, like -r somepath\*.dll -r someotherpath\*.dll and the different paths tend to have duplicates that are harmless. These folks will see wall of warnings with this change.

We do not officially support invoking crossgen manually. You won't run into this with PublishReadyToRun that's our officially supported way to invoke crossgen. I am not sure whether this is worth fixing.

[kg]

Thanks for investigating this. I'll figure out whether it's worth doing the work to actually detect this scenario robustly and generate warnings for it.

[jkotas]

Identical full names do not imply that assembly content is identical. It is very common for two assemblies to have identical full name but have different content. For example., assemblies from given nuget package that target different TFMs have identical full name.

If we want to change how we treat duplicate references, we should disallow or warn on any duplicated simple names, similar how the strict flag works for input assemblies.