Echo build is supported for Raspberry Pi 4 with 4 GB RAM. Ubuntu 18.04 64 bit OS should be installed for Raspberry PI 4.
Echo build is memory-heavy, so a swap space for at least 4 GB should be created. Compiling should be done in one thread/job for the same reason.
To build echo_node and echo_wallet please use following commands. Other targets are not supported yet.
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchains/rpi-native.cmake ..
cmake --build .