srv-shared build on Linux (Ubuntu) fails with /bin/bash: rustup: command not found

[criticaltv]

Describe the bug

When running these instructions, the build process fails with:

[CC] lnx/x86_64 source/server.cpp
rustup target add x86_64-unknown-linux-gnu
/bin/bash: rustup: command not found
make: *** [env/output.mk:197: out-lnx/x86_64-unknown-linux-gnu.rustup] Error 127

cc @saurik

[saurik]

Install rustup.