Split out buck2 CI to a more frequent Actions job

Many commits are landed to the buck2 prelude throughout the day.

.github/workflows/buck2.yml

@@ -0,0 +1,30 @@
+name: Buck2
+
+on:
+  push:
+  workflow_dispatch:
+  schedule: [cron: "40 1,13 * * *"]
+
+permissions:
+  contents: read
+
+jobs:
+  buck2:
+    name: Buck2 on ${{matrix.os == 'ubuntu' && 'Linux' || matrix.os == 'macos' && 'macOS' || matrix.os == 'windows' && 'Windows' || '???'}}
+    runs-on: ${{matrix.os}}-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu, macos, windows]
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rust-src
+      - uses: dtolnay/install-buck2@latest
+      - name: Update buck2-prelude submodule
+        run: git submodule update --init --remote --no-fetch --depth 1 --single-branch tools/buck/prelude
+      - run: buck2 run demo
+      - run: buck2 build ...
+      - run: buck2 test ...

.github/workflows/ci.yml

@@ -70,27 +70,6 @@ jobs:
         env:
           RUSTFLAGS: --cfg compile_error_if_alloc --cfg cxx_experimental_no_alloc ${{env.RUSTFLAGS}}
 
-  buck:
-    name: Buck2 on ${{matrix.os == 'ubuntu' && 'Linux' || matrix.os == 'macos' && 'macOS' || matrix.os == 'windows' && 'Windows' || '???'}}
-    runs-on: ${{matrix.os}}-latest
-    if: github.event_name != 'pull_request'
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu, macos, windows]
-    timeout-minutes: 45
-    steps:
-      - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          components: rust-src
-      - uses: dtolnay/install-buck2@latest
-      - name: Update buck2-prelude submodule
-        run: git submodule update --init --remote --no-fetch --depth 1 --single-branch tools/buck/prelude
-      - run: buck2 run demo
-      - run: buck2 build ...
-      - run: buck2 test ...
-
   reindeer:
     name: Reindeer
     runs-on: ubuntu-latest