Manually adding sdk for AWS SDK PHP Module
Assuming you have git installed, you should be able to run the following from within your /sites/all/libraries directory:

git clone git://github.com/amazonwebservices/aws-sdk-for-php.git awssdk


Alternatively, you could use the Zip button on the Github project page or the link it points to to download the zip file and put it in a subdirectory of libraries directory called awssdk.