SWPROT-8953: docker: Support custom UnifySDK dep

This change is useful for testing other forks (public or private with PAT),
for example:

  docker \
        build \
        --build-arg UNIFYSDK_GIT_REPOSITORY="https://<TOKEN>@github.com/rzr/UnifySDK" \
        --build-arg UNIFYSDK_GIT_TAG="devel/main" \
        .

Forwarded: #10
Signed-off-by: Philippe Coval <philippe.coval@silabs.com>

Author: rzr

Dockerfile

@@ -4,6 +4,9 @@ ENV DEBIAN_FRONTEND noninteractive
 ENV LC_ALL en_US.UTF-8
 ENV LANG ${LC_ALL}
 
+ARG UNIFYSDK_GIT_REPOSITORY https://github.com/SiliconLabs/UnifySDK
+ARG UNIFYSDK_GIT_TAG main
+
 RUN echo "# log: Configuring locales" \
   && set -x  \
   && apt-get update -y \