[llvm] [workflows] Add a new workflow for testing release branch CI (PR #81073)

[Tom Stellard via llvm-commits]

https://github.com/tstellar created https://github.com/llvm/llvm-project/pull/81073

Since we commit all changes to the release branch CI to main first, we need someway to test that these changes to main don't break the CI.

>From a03e5489a11b6adcb3efc602150fe9483d2d47c3 Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar at redhat.com>
Date: Wed, 7 Feb 2024 17:24:30 -0800
Subject: [PATCH] [workflows] Add a new workflow for testing release branch CI

Since we commit all changes to the release branch CI to main first, we
need someway to test that these changes to main don't break the CI.
---
 .../workflows/llvm-project-workflow-tests.yml | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 .github/workflows/llvm-project-workflow-tests.yml

diff --git a/.github/workflows/llvm-project-workflow-tests.yml b/.github/workflows/llvm-project-workflow-tests.yml
new file mode 100644
index 00000000000000..e65a3e86ec32dc
--- /dev/null
+++ b/.github/workflows/llvm-project-workflow-tests.yml
@@ -0,0 +1,31 @@
+# This workflow will test the llvm-project-tests workflow in PRs
+# targetting the main branch.  Since this workflow doesn't normally
+# run on main PRs, we need some way to test it to ensure new updates
+# don't break it.
+
+name: LLVM Workflow Test
+
+permissions:
+  contents: read
+
+on:
+    branches:
+      - 'main'
+    paths:
+      - '.github/workflows/llvm-project-tests.yml'
+      - '.github/workflows/llvm-project-workflow-tests.yml'
+
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: only if it is a pull request build.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
+jobs:
+  llvm-test:
+    if: github.repository_owner == 'llvm'
+    name: Build and Test
+    uses: ./.github/workflows/llvm-project-tests.yml
+    with:
+      build_target: check-all
+      projects: clang;lld;libclc;lldb