build-unit-test-docker: Add .wgetrc for proxy

The script now uses `wget -O - https://apt.llvm.org/llvm.sh` to download
the llvm.sh.

If http_proxy is set, set the proxy to .wgetrc in the docker container
so that it could be used by `wget` when building the unit test docker.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I5cb305515cb4f79e5fd759bf1844a110f106a049
1 file changed