make github actions more forgiving of slow builds

Although we've improved the average build time with caching, it
can still be slow in the worst case, causing the job to time out.

Author: MatMoore

.github/workflows/stage-3-build.yaml

@@ -46,7 +46,7 @@ jobs:
   build:
     name: 'Build'
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 5
     permissions:
       contents: read
       packages: write