NCS 2.4 uses Zephyr 0.16.0

[coderbyheart]

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/getting_started/installing.html#install-the-zephyr-sdk

See #66

[vChavezB]

Just to add to this discussion

This is what I came up with (disclaimer I am by no means a bash expert so there could be an easier way)

major_version=$(echo "${ZEPHYR_TOOLCHAIN_VERSION}" | cut -d. -f1) && 
minor_version=$(echo "${ZEPHYR_TOOLCHAIN_VERSION}" | cut -d. -f2) && 
patch_version=$(echo "${ZEPHYR_TOOLCHAIN_VERSION}" | cut -d. -f3) && 
if test "$major_version" -gt 0 -o "$minor_version" -gt 16 -o "$minor_version" -eq 16 -a "$patch_version" -ge 0; then 
RELEASE_EXTENSION=xz ; 
else 
RELEASE_EXTENSION=gz ; 
fi
ZEPHYR_TOOLCHAIN_URL=${ZEPHYR_TOOLCHAIN_BASE_URL}.${RELEASE_EXTENSION}