OS: Ubuntu 18.04,64bit (New Installed)
Zephyr Version: 2.2.99
Zephyr SDK Version: 0.11.2
xtensa-esp32-elf-gcc Version: 5.2.0 --build=x86_64-build_pc-linux-gnu

As per getting started guide for Zephyr and esp, I have set environment variable. 

export ZEPHYR_TOOLCHAIN_VARIANT="espressif"
export ESPRESSIF_TOOLCHAIN_PATH="/home/swapna/Documents/Workspace/esp/xtensa-esp32-elf"
export ZEPHYR_SDK_INSTALL_DIR="/home/swapna/Documents/Workspace/Zephyr_ESP/zephyr-sdk" 

While building hello_world application using west command:  $west build -b esp32 samples/hello_world

It's getting failed. Attaching output of above command in the file.