by default all cores are used
hoping this will fix the hydra i686 squashfs build issues as all the
failures were using 64 cores
Parallel mksquashfs: Using 64 processors
Creating 4.0 filesystem on ..., block size 1048576.
FATAL ERROR: mangle2:: xz compress failed with error code 5
the nix store may contain hardlinks: derivations may output them
directly, or users may be using store optimization which automatically
hardlinks identical files in the nix store.
The presence of these links are intended to be a 'transparent'
optimization. However, when creating a squashfs image, the image
will be different depending on whether hard links were present
on the filesystem, leading to reproducibility problems.
By passing '-no-hardlinks' to mksquashfs the files are stored
as duplicates in the squashfs image. Since squashfs has support
for duplicate files this does not lead to a larger image.
For more details see
https://github.com/NixOS/nixpkgs/issues/114331
