refactor: Gem update steps now in a script

Gemfile.lock

@@ -79,7 +79,7 @@ GEM
     autoprefixer-rails (10.4.7.0)
       execjs (~> 2)
     aws-eventstream (1.2.0)
-    aws-partitions (1.586.0)
+    aws-partitions (1.587.0)
     aws-sdk-core (3.130.2)
       aws-eventstream (~> 1, >= 1.0.2)
       aws-partitions (~> 1, >= 1.525.0)
@@ -169,7 +169,7 @@ GEM
     listen (3.7.1)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    loofah (2.17.0)
+    loofah (2.18.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -212,7 +212,7 @@ GEM
       activesupport
       bunny
     nio4r (2.5.8)
-    nokogiri (1.13.5)
+    nokogiri (1.13.6)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     pg (1.3.5)
@@ -345,7 +345,7 @@ GEM
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
     strings-case (0.3.0)
-    strscan (3.0.1)
+    strscan (3.0.3)
     thor (1.2.1)
     thread_safe (0.3.6)
     tilt (2.0.10)

README.md

@@ -11,7 +11,7 @@ To update the gems in this core image, great care must be taken. Once the gemfil
 updated with a simple helper script. There are many ways of achieving this, but the recommended way is:
 
 ```
-docker run -it -v "$(pwd)":/app -v /usr/local/bundle:/usr/local/bundle ruby:2.7.5 sh -c "apt-get update; apt-get install -y cmake build-essential; cd /app; gem install bundler:2.1; bundle update; bundle install;"
+./gem-update.sh
 ```
 
 Once both the `Gemfile` and `Gemfile.lock` files are both updated, a commit can be created to force a new update.

gem-update.sh

+#!/bin/bash
+cd "$(dirname "$0")"
+set -ex
+docker run -it -v "$(pwd)":/app \
+  -v /usr/local/bundle:/usr/local/bundle ruby:2.7.5 sh \
+  -c "apt-get update; \
+      apt-get install -y cmake build-essential; \
+      cd /app; \
+      gem install bundler:2.1; \
+      bundle update; \
+      bundle install;"