Add script to setup AWS environment variables

overlays/configure_aws_creds.nix

@@ -2,11 +2,11 @@
 let
 	bw = "${pkgs.bitwarden-cli}/bin/bw";
 
-in pkgs.writeScriptBin "configure_aws_creds" ''
+in pkgs.writeShellScriptBin "configure_aws_creds" ''
 set -ex -o pipefail
 
 session="$(${bw} unlock | grep -e '$ export' | awk -F\" '{print $2}')"
-export BW_SESSION="${session}"
+export BW_SESSION="''${session}"
 export AWS_ACCESS_KEY_ID="$(${bw} get username "AWS Access Key")"
 export AWS_SECRET_ACCESS_KEY="$(${bw} get password "AWS Access Key")"
 ''