SE-0238 関連はあんまり議論がなさげですね... 同様の仕組みを使っている SE-0273 とかまで含めて探せばまだあるかもしれませんが． https://forums.swift.org/t/se-0238-package-manager-target-specific-build-settings/18341 ~~ただ，今回の例に限っては .define("CMARK_THREADING", to: "0", .when(platforms: [.wasi])) で上書きすればいけるような気もしてきました．~~ (ダメでした) (edited)

SE-0238: Package Manager Target Specific Build Settings

Hello Swift community, The review of SE-0238 “Package Manager Target Specific Build Settings" begins now and runs through December 4, 2018. Reviews are an important part of the Swift evolution process. All reviews should be made in this thread on the Swift forums or, if you would like to keep your feedback private, directly in email to me as t...