This has been moved to the Matrix AI blog: https://matrix.ai/2018/03/24/developing-with-nix/
Note that if you just to compile a simple C program, and you don't want to fiddle with environments:
nix-shell --packages stdenvThat's enough to enter an environment with stdenv.
@danbst You are right. You do need
unset SOURCE_DATE_EPOCHin theshellHookfor Python packages.