@crujzo, I am in the exact same position you were in. I have followed @pavanbachu 's instructions:
My path here:
/usr/local/lib/node_modules/appium/node_modules/appium-xcuitest-driver/WebDriverAgent/
Only lists:
npmignore
.travis.yml
CONTRIBUTING.md
Cartfile
Cartfile.resolved
Inspector/
LICENSE
PATENTS
PrivateHeaders/
README.md
Scripts/
WebDriverAgent.xcodeproj/
WebDriverAgentLib/
WebDriverAgentRunner/
WebDriverAgentTests/
WebDriverAgentUSBClient/
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.