Hmmm. Still seeing the issue.
Confirmed from build log that it's using the Dec 3 master trunk snapshot:
/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2019-12-03-a.xctoolchain/usr/bin/swiftc
repo is here if you want to try:
https://github.com/haikusw/testwlbug
I just build it (inside Xcode so as to make selecting the toolchain easy) and then execute the built object in Terminal from within the DerivedData Build folder.
You have to build and run it (or at least run it…) on macOS 10.14.6 (or macOS < 10.15.x) for the CryptoKit dylib to be missing and thus see the problem which is:
dyld: Library not loaded: /System/Library/Frameworks/CryptoKit.framework/Versions/A/CryptoKit
Referenced from: /Users/haikuty/Desktop/testwlbug 2019-12-04 13-18-42/Products/usr/local/bin/testwlbug
Reason: image not found
Abort trap: 6
I'm using Xcode Version 11.2.1 (11B500) running in macOS 10.14.6 (18G103).