I get this error when I try to add the 2 frameworks(Alamofire & AlamofireImage) to my WatchKit Extension target. It actually does not matter from which platform Build folder I will add the frameworks. It always shows the same error.
ld: building for watchOS simulator, but linking against dylib built for iOS, file '/Some-Project-Filder/Carthage/Build/iOS/AlamofireImage.framework/AlamofireImage' for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
That's probably because you have Carthage/iOS in the FRAMEWORK_SEARCH_PATHS setting of your watchOS target.
That was the problem. Sorry for the noob question!
@ivan-konov no need to apologize! Xcode should not require us to configure all this stuff manually.

The "paths" build settings are always a tricky matter I just forgot to check it. Every time I have such a problem I think I should file a radar to Apple so they create separate UI for that! :D
Thanks again!
Spent 1h looking for the cause of this error and kept going in circles with carthage's copy-frameworks step... Thanks @NachoSoto!
Most helpful comment
That's probably because you have
Carthage/iOSin theFRAMEWORK_SEARCH_PATHSsetting of yourwatchOStarget.