[SOLVED] Swift Version Conflict: this SDK is not supported by the compiler, Please select a toolchain which matches the SDK

Swift Version Conflict: this SDK is not supported by the compiler, Please select a toolchain which matches the SDK

I'm using xCode 13.1 with macOS 12.0.1 Monterey. I added KingFisher and removed it from my pod. but my project is not built anymore. I got this error for one of my local SDKs:

Failed to build module 'CbSdk';
this SDK is not supported by the compiler (the SDK is built with 'Apple Swift version 5.4
(swiftlang-1205.0.26.9 clang-1205.0.19.55)', while this compiler is 'Apple Swift version 5.5.1 
(swiftlang-1300.0.31.4 clang-1300.0.29.6)'). Please select a toolchain which matches the SDK.

What I've done but didn't work:

pod deintegrate and pod install.
restart xCode with clearing cache and DerivedData.
checkout old branch and commit that worked before.
moving code to another macBook that worked before.
download, install and select toolchain 5.4 (odd errors appeared -> )
changing swift compiler language of my target and project to swift 4 (It says you are using swift 5.5.1 again!)
note that I didn't update xcode or swift!

Solution

Taken from this Twitter thread.

You need to set the BUILD_LIBRARY_FOR_DISTRIBUTION build setting on the framework target

https://www.swift.org/blog/library-evolution/

https://developer.apple.com/videos/play/wwdc2019/416/