Install toolchain

mkdir ~/esp32

cd ~/esp32

wget https://dl.espressif.com/dl/xtensa-esp32-elf-osx-1.22.0-80-g6c4433a-5.2.0.tar.gz

tar xvfz xtensa-esp32-elf-osx-1.22.0-80-g6c4433a-5.2.0.tar.gz 

rm *.gz

Add toolchain to your path

vi ~/.profile

export PATH=$PATH:$HOME/esp32/xtensa-esp32-elf/bin

Install ESP-IDF

cd ~/esp32

git clone -b v3.1.1 --recursive https://github.com/espressif/esp-idf.git

Add IDF_PATH environment variable

vi ~/.profile

export IDF_PATH=~/esp32/esp-idf

Reference