wip nightly cronjob CI

.github/workflows/build-test.yml

@@ -18,13 +18,29 @@ on:
     branches: [ main ]
   pull_request:
     branches: '*'
+  workflow_dispatch:
+    inputs:
+      nightly:
+        description: "Test on latest nightly"
+        required: true
+        default: false
+        type: boolean
+  schedule:
+    # Run nightly cronjob CI every day at 14 UTC / 6AM PST / 3PM CET
+    - cron:  '0 14 * * *'
 
 jobs:
 
   # Build job - basic smoke test
   check:
     runs-on: ubuntu-latest
     steps:
+    - name: Set the rust toolchain to use
+    # pull_request is a fake for me to be able to test this for now
+    - if: "github.event.schedule || github.event.pull_request || (github.event.workflow_dispatch && inputs.nightly)"
+    - run: |
+        rustup default nightly
+        echo "ICU4X_NIGHTLY_TOOLCHAIN=nightly" >> >> $GITHUB_ENV
     - uses: actions/checkout@v2
     - name: Load the default Rust toolchain via the rust-toolchain file.
       run: rustup show