Carthage run script phase - for Xcode

#!/bin/sh
# Script used in XCode build phase to bring Carthage dependencies up to date
#  Will check if the Cartfile is newer than the Cartfile.resolved, and if so
#   Will bring the Carthage checkouts up to date
#  If the checkouts are newer than the build
#   Will bring the build up to date
#
# Derek Knight
# Jun 2016

if [ -z "$CONFIGURATION" ]; then
	CONFIGURATION="Release"
fi
if [ -z "$PLATFORM" ]; then
	PLATFORM="iOS"
fi

if [ "Cartfile" -nt "Cartfile.resolved" ]; then
  echo "Cartfile is newer than source, removing source"
  rm -rf Carthage/Checkouts
fi

if ! [ -d "Carthage/Checkouts" ]; then
	echo "Source doesn't exist, checking out"
    env -i /usr/local/bin/carthage update --no-build --platform $PLATFORM --configuration $CONFIGURATION $*
    rm -rf Carthage/Build/$PLATFORM
fi

if [ -d "Carthage/Build/$PLATFORM" ]; then
  echo "$PLATFORM Build exists"
else
  echo "Build doesn't exist, building"
  env -i /usr/local/bin/carthage build --platform $PLATFORM --configuration $CONFIGURATION $*
fi

I save this as /usr/local/bin/carthage-xcode, then my Xcode run Script task "Update/Build Carthage Dependencies" is just one line:

/usr/local/bin/carthage-xcode