Fix zsh Incompatibility in Spack Environment Activation

[EnekoGonzalez3]

The deployment script's use of the -p flag with spack env activate causes issues in zsh, as it fails to determine the interactive shell prompt. Changing the if statement in build.sh and install.sh to use eval $(spack env activate --sh "${REPO_ROOT}") resolves this issue. This change supports sh, bash, and zsh and has been successfully tested locally.