I see that there are several other questions regarding this problem.
Like: Xcode 10 Error: Multiple commands produce
I am asking this a new because it is for Xcode 11.1 and not older version and I think that the other questions have too many responses and people easily can get lost in them. Here we can try to answer using newer information with quicker access.
After update to Xcode 11.1 and update of cocoa pods ( no pods were actually updated, only the pods project was regenerated ).
I started to get the following error with FBSDK:
Multiple commands produce '/Users/myUser/Library/Developer/Xcode/DerivedData/myProject-euqkymjpeftprkgkcjyqpnkbalbr/Build/Products/Debug-iphoneos/FBSDKCoreKit-iOS/FBSDKCoreKit.framework/PrivateHeaders/FBSDKRestrictiveDataFilterManager.h':
1) Target 'FBSDKCoreKit-iOS' (project 'Pods') has copy command from '/Users/myUser/Documents/Workspace/myProjectDir/Pods/FBSDKCoreKit/FBSDKCoreKit/FBSDKCoreKit/AppEvents/Internal/FBSDKRestrictiveDataFilterManager.h' to '/Users/myUser/Library/Developer/Xcode/DerivedData/myProject-euqkymjpeftprkgkcjyqpnkbalbr/Build/Products/Debug-iphoneos/FBSDKCoreKit-iOS/FBSDKCoreKit.framework/PrivateHeaders/FBSDKRestrictiveDataFilterManager.h'
2) Target 'FBSDKCoreKit-iOS' (project 'Pods') has copy command from '/Users/myUser/Documents/Workspace/myProjectDir/Pods/FBSDKCoreKit/FBSDKCoreKit/FBSDKCoreKit/AppEvents/Internal/RestrictiveDataFilter/FBSDKRestrictiveDataFilterManager.h' to '/Users/myUser/Library/Developer/Xcode/DerivedData/myProject-euqkymjpeftprkgkcjyqpnkbalbr/Build/Products/Debug-iphoneos/FBSDKCoreKit-iOS/FBSDKCoreKit.framework/PrivateHeaders/FBSDKRestrictiveDataFilterManager.h'