Override nightly versions if repo variable set for non scheduled runs (#524)

- [x] no changelog update needed

.github/workflows/build-and-test.yml

@@ -2,14 +2,15 @@ name: Rust
 
 on:
   push:
-    branches: [ master ]
+    branches: [master]
   pull_request:
-    branches: [ master ]
+    branches: [master]
   schedule:
-    - cron: '10 6 * * *'
+    - cron: "10 6 * * *"
 
 env:
   CARGO_TERM_COLOR: always
+  RUSTUP_TOOLCHAIN: ${{ !github.event.schedule && 'nightly-2023-12-01' || 'nightly' }}
 
 jobs:
   build:
@@ -22,8 +23,7 @@ jobs:
         run: sudo apt-get update && sudo apt-get install build-essential libelf-dev zip -y
       - name: Install Miri
         run: |
-          rustup toolchain install nightly --component miri
-          rustup override set nightly
+          rustup component add miri clippy rustfmt
           cargo miri setup
       - uses: actions/checkout@v4
       - name: Cache
@@ -40,7 +40,7 @@ jobs:
       - name: Setup mdBook
         uses: peaceiris/actions-mdbook@v1
         with:
-        mdbook-version: '0.4.13'
+          mdbook-version: "0.4.13"
       - name: Build and test all crates
         run: just ci
       - name: Upload build artifacts