Archiving a project containing Swift static libraries is broken in Xcode 10 beta 3

Radar: 41773389 (submitted by a colleague, reposting here)

Summary:

Archiving a project that includes a Swift static library referencing ObjC types within system frameworks (e.g. NSObject, NSURLSessionDelegate) causes udefined symbol errors (e.g. Undefined symbols for architecture arm64: "l003", referenced from:...) when linking in Xcode 10 beta.

Steps to Reproduce:

• Create a new Xcode project (sample attached)
• Create a new (Swift) static library (either .a or .framework wrapper with Mach-O Type set to Static Library)
• Ensure the main application target links in the static library
• Within the static library attempt to subclass or conform to an ObjC system framwork type (e.g. NSObject, NSURLSessionDelegate)
• Archive the project

Expected Results:

Project should archive successfully (like it did when using Xcode 9)

Actual Results:

A linker error occurrs:

Undefined symbols for architecture arm64: "l003", referenced from: _$S18StaticSwiftLibrary02MyaC5ClassCMn in libStaticSwiftLibrary.a(StaticSwiftLibrary.o) ld: symbol(s) not found for architecture arm64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

Version/Build:

Version 10.0 beta 3

Notes:

• We're seeing various "l00x" codes based on which type is used in the static library
• This occurs with both the old and new build system

The radar has a full sample project attached. For the purposes of this post, the Swift static library just needs to contain this:

public class MyStaticLibraryClass: NSObject {
   
}

$ swift-demangle S18StaticSwiftLibrary02MyaC5ClassCMn
$S18StaticSwiftLibrary02MyaC5ClassCMn ---> nominal type descriptor for StaticSwiftLibrary.MyStaticLibraryClass

So we're guessing the type info for the class is trying to reference some kind of auto-generated incremening L00X symbol representing any ObjC types used, or something?