nixos ec2/create-amis.sh: shellcheck: explicitly make the additions to block_device_mappings single strings
nixos ec2/create-amis.sh: shellcheck: explicitly make the additions to block_device_mappings single strings

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs