@crujzo, I am in the exact same position you were in. I have followed @pavanbachu 's instructions:
My path here:
As you can see, Carthage is not there. It is installed at /usr/local/Cellar/
I have uninstalled and reinstalled Appium, I have uninstalled and reinstalled Carthage through both npm and brew, to no avail.
The .xcconfig file I have created under WebDriverAgent is not being recognized. I am on appium --version 1.6.3. I would greatly appreciate any help.