treewide: remove FHSEnv

To remove the FHSenv, we have to patch rules_python to use
/usr/bin/env to resolve the path to bash instead of hardcoding it.
Additionally, we now bring a Nix-compatible Bazel 8.

Change-Id: Id51e7748eea6dd77185f43a52fe45b5110ba4a2b
Reviewed-on: https://review.monogon.dev/c/monogon/+/4427
Tested-by: Jenkins CI
Reviewed-by: Jan Schär <jan@monogon.tech>
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/third_party/nix/default.nix b/third_party/nix/default.nix
index eab83d7..726119e 100644
--- a/third_party/nix/default.nix
+++ b/third_party/nix/default.nix
@@ -9,6 +9,7 @@
           util-linux-minimal = import ./pkgs/util-linux { pkgs = super; };
           bazel-unwrapped = import ./pkgs/bazel { pkgs = super; };
           perl = import ./pkgs/perl { pkgs = super; };
+          bazel_8 = self.callPackage ./pkgs/bazel_8/package.nix { };
           python3Minimal = import ./pkgs/python3 { pkgs = super; };
           bison = import ./pkgs/bison { pkgs = super; };
         })