Fixes fj#940.
When running `nix-shell`, the `$NIX_BUILD_TOP` environment variable is
set to `$TMPDIR` or `/tmp`.
nixpkgs stdenv uses $NIX_BUILD_TOP to create `$NIX_BUILD_TOP/env-vars`
which contains all the environment variables set by stdenv. This is used
for debugging purposes in combination with `--keep-failed` to reload the
bash environment of a derivation.
`$TMPDIR` is often unset, therefore, `/tmp/env-vars` was constantly
being created. On a multi-user system or, when you run Lix as root, you
might create a `/tmp/env-vars` with different permission bits.
As a result, `nix-shell` can cease to function because that file will
fail creation for an unprivileged user for example.
fj#940 rightfully remark that the code is not consistent between
nix3-develop and nix-shell and it should be reworked.
Change-Id: Iddf15945385d8bd497b2800b37fee5e1f97689b7
Signed-off-by: Raito Bezarius <raito@lix.systems>
(cherry picked from commit feab75bde0)
Raito Bezarius
9bfef6a06c