tooling: Enable strict shell mode in selected scripts.

Add strict shell options (set -euo pipefail / set -eu) to a small
set of simple shell scripts that do not rely on unset variables
or pipeline exit-code masking.

Each script was reviewed line by line to confirm strict mode is
safe and that stopping immediately on errors is the correct
behavior for these scripts.

Fixes part of #20748.

puppet/zulip/files/letsencrypt/020-symlink.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-
+set -euo pipefail
 symlink_with_backup() {
     if [ -e "$2" ]; then
         # If the user is setting up our automatic certbot-management on a

puppet/zulip/files/letsencrypt/050-nginx.sh

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
-
+set -euo pipefail
 service nginx reload

tools/run-tsc

@@ -1,3 +1,4 @@
 #!/bin/sh
+set -eu
 ZULIP_PATH="$(dirname "$0")/.."
 exec "$ZULIP_PATH/node_modules/.bin/tsc" --project "$ZULIP_PATH" "$@"

tools/setup-git-repo

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+set -euo pipefail
 
 if ! [ -d ".git/hooks/" ]; then
     echo "Error: Could not find .git/hooks directory"