[ethereumproject/go-ethereum] problem: make install/build command fails if rust/cargo not installed (#661)

solution: check for existence of ‘cargo’ command, and if it DOESNT exist
then prompt user to go ahead with rustup installation, otherwise just
exit
You can view, comment on, or merge this pull request online at:

https://github.com/ethereumproject/go-ethereum/pull/661

— Commit Summary —

* problem: make install/build command fails if rust/cargo not installed

— File Changes —

M scripts/build_sputnikvm.sh (19)

— Patch Links —

https://github.com/ethereumproject/go-ethereum/pull/661.patch
https://github.com/ethereumproject/go-ethereum/pull/661.diff