Updates the ruby dockerfile to copy the cacerts directory from the docker host
diff --git a/tools/dockerfile/grpc_ruby/Dockerfile b/tools/dockerfile/grpc_ruby/Dockerfile
index c677cef..f01f81d 100644
--- a/tools/dockerfile/grpc_ruby/Dockerfile
+++ b/tools/dockerfile/grpc_ruby/Dockerfile
@@ -6,6 +6,9 @@
   && git pull --recurse-submodules \
   && git submodule update --init --recursive
 
+# TODO: remove this, once make install is fixed
+RUN touch /var/local/git/grpc/include/grpc/support/string.h
+
 # Build the C core.
 RUN make install_c -C /var/local/git/grpc
 
@@ -18,5 +21,8 @@
 # - however, the interop server and client run OK, so this bug can be investigated
 # RUN /bin/bash -l -c 'cd /var/local/git/grpc/src/ruby && bundle && rake'
 
+# Add a cacerts directory containing the Google root pem file, allowing the ruby client to access the production test instance
+ADD cacerts cacerts
+
 # Specify the default command such that the interop server runs on its known testing port
-CMD ["/bin/bash", "-l", "-c", "ruby /var/local/git/grpc/src/ruby/bin/interop/interop_server.rb --port 8060"]
+CMD ["/bin/bash", "-l", "-c", "ruby /var/local/git/grpc/src/ruby/bin/interop/interop_server.rb --use_tls --port 8060"]