[ci] Pass IP for repo.radeon.com as docker buildargs

docker/dockerfile-hip-ubuntu-16.04

@@ -1,5 +1,6 @@
 # Parameters related to building hip
 ARG base_image
+ARG REPO_RADEON=$REPO_RADEON
 
 FROM ${base_image}
 MAINTAINER Kent Knox <kent.knox@amd>
@@ -9,8 +10,8 @@ COPY *.deb /tmp/
 
 # Install the debian package
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y curl \
-  && curl -sL http://repo.radeon.com/rocm/apt/debian/rocm.gpg.key | apt-key add - \
-  && echo deb [arch=amd64] http://repo.radeon.com/rocm/apt/debian/ xenial main | tee /etc/apt/sources.list.d/rocm.list \
+  && curl -sL http://$REPO_RADEON/rocm/apt/debian/rocm.gpg.key | apt-key add - \
+  && echo deb [arch=amd64] http://$REPO_RADEON/rocm/apt/debian/ xenial main | tee /etc/apt/sources.list.d/rocm.list \
   && apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends --allow-unauthenticated -y \
     /tmp/hip_base-*.deb \
     /tmp/hip_hcc-*.deb \