Spack Install Procedure has changed

The installation procedure for spack has been updated. The spack issue that contains the update is below.

These are the new instructions:

Clone the spack repo
git clone https://github.com/spack/spack.git
Go to spack folder
cd spack
Source spack
source share/spack/setup-env.sh
Clone the spack-package repository
git clone https://github.com/spack/spack-packages.git
Set spack repository destination to currently cloned spack-packages
spack repo set --destination "$(pwd)/spack-packages" builtin
Check if it's working or not
spack info gcc

This information came from [here](https://github.com/spack/spack/issues/50922#issuecomment-3167890275)