試しに.build/x86_64-apple-macosx/debug/ConcurrencyExampleをDeveloper ID Applicationで署名してみましたが、DYLD_LIBRARY_PATHは通りました。

$ swiftnightly build [1/1] Planning build [3/3] Linking ConcurrencyExample * Build Completed! $ codesign -s "Developer ID Application: Norio Nomura (PK9GMQ772L)" .build/debug/ConcurrencyExample $ codesign -vv .build/debug/ConcurrencyExample .build/debug/ConcurrencyExample: valid on disk .build/debug/ConcurrencyExample: satisfies its Designated Requirement $ DYLD_LIBRARY_PATH=~/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2021-01-09-a.xctoolchain/usr/lib/swift/macosx .build/debug/ConcurrencyExample task started { "uuid": "32cf6d86-bb2d-4089-8262-9ecfcf9d7418" } end of main