Also if I try to download SDK using download.sh from https://github.com/gl-inet/sdk it terminates with errors too:
/download.sh ipq807x-2102
Download ipq807x-2102 SDK
Cloning into 'sdk/2102/ipq807x'...
remote: Enumerating objects: 33974, done.
remote: Total 33974 (delta 0), reused 0 (delta 0), pack-reused 33974
Receiving objects: 100% (33974/33974), 262.79 MiB | 7.10 MiB/s, done.
Resolving deltas: 100% (5193/5193), done.
Updating files: 100% (33623/33623), done.
./download.sh: 47: pushd: not found
./download.sh: 48: ./scripts/feeds: not found
./download.sh: 49: ./scripts/feeds: not found
make: *** No rule to make target 'defconfig'. Stop.
./download.sh: 51: popd: not found
Use 'builder.sh script to compile all your packages.
Run './builder.sh' to get more help.