Install maven for macOS

Author: kannanjgithub

buildscripts/kokoro/macos.sh

@@ -23,5 +23,6 @@ trap spongify_logs EXIT
 export -n JAVA_HOME
 brew install --cask temurin@8
 export PATH="$(/usr/libexec/java_home -v"1.8.0")/bin:${DOWNLOAD_DIR}/cmake-${CMAKE_VERSION}-macos-universal/CMake.app/Contents/bin:${PATH}"
+brew install maven
 
 "$GRPC_JAVA_DIR"/buildscripts/kokoro/unix.sh