add more ruby artifact deps

tools/internal_ci/helper_scripts/prepare_build_macos_rc

@@ -27,7 +27,7 @@ brew install gflags
 set +ex  # rvm script is very verbose and exits with errorcode
 source $HOME/.rvm/scripts/rvm
 set -e  # rvm commands are very verbose  
-rvm install ruby-2.3
+rvm install ruby-2.4
 rvm osx-ssl-certs status all
 rvm osx-ssl-certs update all
 set -ex

tools/internal_ci/macos/grpc_build_artifacts.sh

@@ -37,5 +37,12 @@ npm install -g node-gyp
 curl -O http://pear.php.net/go-pear.phar
 sudo php -d detect_unicode=0 go-pear.phar
 
+# needed to build ruby artifacts
+gem install rake-compiler
+wget https://raw.githubusercontent.com/grpc/grpc/master/tools/distrib/build_ruby_environment_macos.sh
+bash build_ruby_environment_macos.sh
+
+gem install rubygems-update
+update_rubygems
 
 tools/run_tests/task_runner.py -f artifact macos