grub: Add mdadm to search path.
grub: Add mdadm to search path.

Grub uses mdadm to find out the device it is on, especially when mdadm itself
resides in a separate boot partition. When bootstrapping from a NixOS
installation CD, it's not a big issue because usually the paths from the Nix
store of the installation CD are matching with the ones in the chrooted
environment.

Signed-off-by: aszlig <ee1aa092358634f9c53f01b5a783726c9e21b35a@redmoonstudios.org>

triton/triton,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,NixOS/nixpkgs,triton/triton,NixOS/nixpkgs,NixOS/nixos,SymbiFlow/nixpkgs,NixOS/nixpkgs,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,andreassalomonsson/nixos,NixOS/nixos,SymbiFlow/nixpkgs,NixOS/nixos,NixOS/nixpkgs,NixOS/nixpkgs,triton/triton,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,andreassalomonsson/nixos,NixOS/nixpkgs,triton/triton,NixOS/nixpkgs,andreassalomonsson/nixos,NixOS/nixos,NixOS/nixpkgs,NixOS/nixpkgs,andreassalomonsson/nixos,SymbiFlow/nixpkgs,triton/triton,SymbiFlow/nixpkgs,SymbiFlow/nixpkgs,triton/triton,NixOS/nixpkgs,NixOS/nixos,NixOS/nixpkgs,triton/triton,SymbiFlow/nixpkgs,andreassalomonsson/nixos,NixOS/nixpkgs,NixOS/nixos,andreassalomonsson/nixos,NixOS/nixpkgs,triton/triton,SymbiFlow/nixpkgs,NixOS/nixpkgs