build-unit-test-docker: Get rid of git clones

It is slower and takes more disk space to clone the entire repo instead
of just using the source archive of the version we want.

Change-Id: I8e36fabf773e9227c5cf91ba906bb9b42baa3405
Signed-off-by: William A. Kennington III <wak@google.com>
1 file changed