If `settings.buildDir` cannot be written to, because we are in a chroot
store, unprivileged or anything.
We can and should always gracefully fallback to a *secure* location
inside of /tmp, i.e. `/tmp/<a directory under 0700>/<our temporary
directory for build under 0700>/...`.
This does not reintroduce CVE-2025-52991 because we are creating a
directory in-between compared to creating only ONE level of directory.
Under macOS, the first level of directory has actually mode 0755 instead
of 0700 as macOS often do not possess the right primitives to chroot
inside of these directories, leading to
https://github.com/NixOS/nix/pull/11031.
Thanks to Emily for the heads-up on this type of matter.
Fixes#876.
Change-Id: Ie521202923f763225e1901ab1b9b6c6132aaf548
Signed-off-by: Raito Bezarius <raito@lix.systems>
Raito Bezarius
22a1d233bb