docker: use smaller image, down anoter 100M

Author: domenkozar

containers/devenv/Dockerfile

@@ -1,8 +1,8 @@
-FROM nixos/nix:latest@sha256:8c144c6c37184fe03fd7fed740c6eeb2ecfd801d6e34a6aba4e38f1c8d10de3e
+FROM nixpkgs/nix:latest
 
 ARG DEVENV_VERSION=latest
 
 # https://github.com/NixOS/nix/issues/5258
-RUN echo "filter-syscalls = false" >> /etc/nix/nix.conf
+RUN mkdir /etc/nix && echo "filter-syscalls = false" >> /etc/nix/nix.conf
 
-RUN nix profile install -j1 github:cachix/devenv/$DEVENV_VERSION --extra-experimental-features 'flakes nix-command' --accept-flake-config && nix-collect-garbage -d
+RUN nix profile install -j1 github:cachix/devenv/$DEVENV_VERSION nixpkgs#gnugrep --extra-experimental-features 'flakes nix-command' --accept-flake-config && nix-collect-garbage -d && rm -rf /root/.cache