Although the OP's original problem seems to be solved, I was nevertheless curious about how to host externally generated tarballs at github (rather than github tarballs generated from github hosted source code). There may be other ways but I figured out a pretty simple method described here.
The target tarball is unittest-cpp-2.0.0.tar.gz which I just happened to have lying around in /tmp for some reason that I don't recall right now. In the local copy of my hoorex project, I made a new branch "testbinary" from which I cleaned out all files and then copied and git added the unittest-cpp-2.0.0.tar.gz file. Of course if you made a dedicated project to do this, you'd just use the master branch. After committing the changes, I pushed the new branch back to github. The direct download by wget of the new external tarball is:
Code:
wget https://github.com/cwilling/hoorex/raw/testbinary/unittest-cpp-2.0.0.tar.gz
i.e. construct the url by first pointing to your project (hoorex, in this case), add "raw" directory, add the branch name directory (testbinary, in this case) and finally add the name of the tarball you previously pushed.
chris