Merge pull request #3547 from matt-kwong/kokoro_mac_build

Remove pre-installed softwares from prebuild steps

kokoro/macos/prepare_build_macos_rc

@@ -17,8 +17,10 @@ export CXX=g++
 # Install Brew and core softwares
 
 ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+source $HOME/.rvm/scripts/rvm
 brew tap homebrew/homebrew-php
-brew install autoconf automake ccache cmake gflags gpg gpg2 libtool maven node pcre php56 ruby wget
+brew uninstall node icu4c
+brew install gflags gpg gpg2 node pcre php56 ruby
 
 ##
 # Install Tox