Use make from homebrew in Mac tests

packages/grpc-native-core/tools/run_tests/artifacts/build_one_artifact_macos.sh

@@ -24,6 +24,8 @@ npm install -g npm
 npm install -g node-gyp
 
 set -ex
+brew install make
+PATH="$(brew --prefix)/opt/make/libexec/gnubin:$PATH"
 cd $(dirname $0)/../../../../..
 base_dir=$(pwd)
 

test/kokoro.sh

@@ -19,6 +19,13 @@ rm -rf ~/.rvm
 set -e
 cd $(dirname $0)/..
 
+OS=$(uname)
+if [ "$OS" = "Darwin" ]
+then
+  brew install make
+  PATH="$(brew --prefix)/opt/make/libexec/gnubin:$PATH"
+fi
+
 # Install gRPC and its submodules.
 git submodule update --init --recursive