Swift Sdtlib tool error: Task failed with exit code 1

I use macOS High Sierra, Xcode 9.3: This worked for me.

1. Go to /Users/JohnAppleseed/Library/Developer/Xcode/DerivedData/
2. Moved all the files to Trash, empty the trash
3. Opened Xcode, Clean and Build.

Restarting xcode or macbook, dragging and dropping certificate in the keychain did not work for me.

Ok so I solved this, don't know if it's the right way or not.

Moved my iOS developer certificate from local to system using Key Chain.

Steps:

1. Close Xcode.
2. Open Key Chain.
3. Find the iOS Developer cert in Local.
4. Drag and drop the cert from Local to the System tab.
5. Enter admin password when prompted.
6. Start Xcode and build project for your device.