See #62956 for work done in .NET 8 for adding AssemblyBuilder.Save(string/stream) support. Remaining work include:

• Add new ILGenerator implementation
  • Initial ILGenerator implementation, save minimal/simple IL.
  • Calculate the maxstack appropriately
  • Add support for emitting a call to method, constructor, field, type references
  • Add local variables support
  • Add label (branching) support
  • Add Try/Catch/Finally/Filter/Fault block support
  • Add support for remaining Emit APIs (EmitCall, EmitCalli, Emit Signatures)
• Add support for remaining members
  • Add ConstructorBuilderImpl and save it to file/stream (this should include Emit(OpCode opcode, ConstructorInfo con) implementation)
  • Add PropertyBuilderImpl and save it to file/stream
  • Add EventBuildterImpl and save it to file/stream
  • Add implementation for remaining unimplemented APIs in AssemblyBuilder/ModuleBuilder (CreateGlobalFuntions, DefineGlobalMethod etc)
  • Add implementation for remaining unimplemented APIs for a MethodBuilder/TypeBuilder/FieldBuilder (like SignatureCallingConvention, *RequiredCustomModifiers, *OptionalCustomModifiers)
• Add approved public APIs: Add public APIs for persisted AssemblyBulder #97177
• Entry point support
  • Get API shape approved and implemented
• Add PDBs support
  • Prototype possible solutions to make the design decisions and propose API shape, get proposal approved
  • Implementation and testing