Updates workflow and build script

Updates workflow to use actions with Node.js 20

Updates build script to fail the build on CI if stack attempts to write
a new lock file.

.github/workflows/main.yml

@@ -14,10 +14,10 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-version: v3
         with:

scripts/test

@@ -4,8 +4,16 @@ set -e
 
 source scripts/lib/run-in-container.sh
 
+STACK_OPTIONS=""
+
+if [ "$CI" ]; then
+  STACK_OPTIONS="--lock-file error-on-write"
+else
+  STACK_OPTIONS="--fast"
+fi
+
 stack \
   build \
   --test \
-  --fast \
+  $STACK_OPTIONS \
   "$@"