Add -optimistic for crossgen2 option --instruction-set.

[viewizard]

Could be used for compile on x64 host for arm64 target (for example, during Tizen OS image creation).

Related to #121175, another approach for disable optimistic instruction set to be added.

CC @gbalykov @tannergooding @MichalStrehovsky

[am11]

It would be nice to also update the help text with native and optimistic options (ilc --help, crossgen2 --help):

runtime/src/coreclr/tools/aot/ILCompiler/ILCompilerRootCommand.cs

Lines 356 to 385 in 9451b1f

	Console.WriteLine("The allowable values for the --instruction-set option are described in the table below. Each architecture has a different set of valid " +
	"instruction sets, and multiple instruction sets may be specified by separating the instructions sets by a ','. For example 'avx,aes,apx'");
	foreach (string arch in ValidArchitectures)
	{
	TargetArchitecture targetArch = Helpers.GetTargetArchitecture(arch);
	bool first = true;
	foreach (var instructionSet in Internal.JitInterface.InstructionSetFlags.ArchitectureToValidInstructionSets(targetArch).DistinctBy((instructionSet) => instructionSet.Name, StringComparer.OrdinalIgnoreCase))
	{
	// Only instruction sets with are specifiable should be printed to the help text
	if (instructionSet.Specifiable)
	{
	if (first)
	{
	Console.Write(arch);
	Console.Write(": ");
	first = false;
	}
	else
	{
	Console.Write(", ");
	}
	Console.Write(instructionSet.Name);
	}
	}
	if (first) continue; // no instruction-set found for this architecture
	Console.WriteLine();
	}

and

runtime/src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.cs

Lines 316 to 343 in 9451b1f

	Console.WriteLine(SR.InstructionSetHelp);
	foreach (string arch in ValidArchitectures)
	{
	TargetArchitecture targetArch = Helpers.GetTargetArchitecture(arch);
	bool first = true;
	foreach (var instructionSet in Internal.JitInterface.InstructionSetFlags.ArchitectureToValidInstructionSets(targetArch).DistinctBy((instructionSet) => instructionSet.Name, StringComparer.OrdinalIgnoreCase))
	{
	// Only instruction sets with are specifiable should be printed to the help text
	if (instructionSet.Specifiable)
	{
	if (first)
	{
	Console.Write(arch);
	Console.Write(": ");
	first = false;
	}
	else
	{
	Console.Write(", ");
	}
	Console.Write(instructionSet.Name);
	}
	}
	if (first) continue; // no instruction-set found for this architecture
	Console.WriteLine();
	}

[viewizard]

It would be nice to also update the help text with native and optimistic options (ilc --help, crossgen2 --help):

Good point, thanks! Added.

[jkotas]

/ba-g infrastructure timeouts