Carthage and GoogleMap

According to Carthage docs:

The only supported origins right now are GitHub repositories (both GitHub.com and GitHub Enterprise)

Carthage actually builds binary framework from the sources it checkouts from the specified repository. Developer needs to link this built binary frameworks to the project afterwards.

Google already provides you with the binary version of GoogleMaps framework instead of sharing sources. Therefore all you have to do is just download this binary from official website and link it to your project without using Carthage. So you can say that Google has already done Carthage work for you so you don't have to use Carthage to build GoogleMap framework. And I believe you even couldn't if you want to because GoogleMaps source code is not open.

Hope my answer will be helpful for you.

Carthage supports linking directly to binary assets. If you go to the "Manual Integration" section in the documentation page, you'll notice the download link looks something like this:

https://dl.google.com/dl/cpdc/d308af63f78a5a1a/GoogleMaps-3.1.0.tar.gz

So all you have to do is create a local JSON file called something like GoogleMaps.json, and put the following in it:

{
  "3.1.0" : "https://dl.google.com/dl/cpdc/d308af63f78a5a1a/GoogleMaps-3.1.0.tar.gz"
}

Then, in your Cartfile, add:

binary "GoogleMaps.json" ~> 3.1.0

Voila!