ci: ignore tldraw.new build script (tldraw#8731)

### Change type

- [ ] `bugfix`
- [ ] `improvement`
- [ ] `feature`
- [ ] `api`
- [x] `other`

Author: mimecuvalo

apps/tldraw-new/vercel.json

@@ -1,4 +1,5 @@
 {
+	"ignoreCommand": "bash ../../internal/scripts/vercel/should-build-tldraw-new.sh",
 	"redirects": [
 		{
 			"source": "/(.*)",

internal/scripts/vercel/should-build-tldraw-new.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -eux
+
+SCRIPT_DIR=$(dirname "$0")
+REPO_ROOT=$(realpath "$SCRIPT_DIR/../../..")
+cd "$REPO_ROOT"
+
+if [[ "$VERCEL_ENV" == "production" ]] ; then
+  echo "Always build on production";
+  exit 1;
+fi
+
+## main is not production anymore, but we still always want to build it
+if [[ "$VERCEL_GIT_COMMIT_REF" == "main" ]] ; then
+  echo "Always build on main";
+  exit 1;
+fi
+
+## on PR builds, only rebuild if the tldraw-new directory changed
+git diff HEAD^ HEAD --quiet -- "./apps/tldraw-new/"