Alamofire has been working fine for an iPhone only project.
I DID THE MANUAL INSTALL OF ALAMOFIRE - NOT COCOA PODS
Now I have added a watch app target following
Below 2 steps have resolved above issue :
i) Check the target name in the Podfile it should match with extension that you are adding Library to it. "AppleWatchApp Extension" instead of "AppleWatchApp" in my case .
ii) Change the framework search Path in BUILD SETTINGS in the target as mention below.