[llvm] [CI] Add Github actions job to build LLVM documentation (PR #69269)

[Tom Stellard via llvm-commits]

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@@ -0,0 +1,43 @@
+# LLVM Documentation CI
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+name: "Test documentation build"
+
+on:
+  push:
+    branches:
+      - 'main'
+    paths:
+      - 'llvm/docs/**'
+  pull_request:
+    paths:
+      - 'llvm/docs/**'
+
+jobs:
+  check-docs-build:
+    name: "Test documentation build"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fetch LLVM sources
+        uses: actions/checkout at v4
+        with:
+          fetch-depth: 2
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tstellar wrote:

Why 2 here?

https://github.com/llvm/llvm-project/pull/69269