As far as I can tell, there's no harm to let stdenv know that they can write to file descriptor 2 which is stderr inside of a nix3-develop shell. Contributes towards #336. Change-Id: I51dcbcbc19a1698a0d1255f9d943d9ebd15d115d Signed-off-by: Raito Bezarius <raito@lix.systems>