[llvm] [workflows] Port buildkite Windows config to GitHub actions (PR #82093)

[Martin Storsjö via llvm-commits]

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@@ -0,0 +1,220 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===##
+#
+# 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
+#
+#===----------------------------------------------------------------------===##
+
+#
+# This file generates a Buildkite pipeline that triggers the various CI jobs for
+# the LLVM project during pre-commit CI.
+#
+# See https://buildkite.com/docs/agent/v3/cli-pipeline#pipeline-format.
+#
+# As this outputs a yaml file, it's possible to log messages to stderr or
+# prefix with "#".
+
+
+set -eu
+set -o pipefail
+
+# Environment variables script works with:
+
+# Set by GitHub
+: ${GITHUB_OUTPUT:=}
+: ${RUNNER_OS:=}
+
+# Allow users to specify which projects to build.
+all_projects="bolt clang clang-tools-extra compiler-rt cross-project-tests flang libc libclc lld lldb llvm mlir openmp polly pstl"
+if [ "$#" -ne 0 ]; then
+  wanted_projects="${@}"
+else
+  wanted_projects="${all_projects}"
+fi
+
+# List of files affected by this commit
+: ${MODIFIED_FILES:=$(git diff --name-only HEAD~1...HEAD)}
----------------
mstorsjo wrote:

How does this work, when a branch contains multiple commits (e.g. an original one and multiple corrections/tweaks) - essentially we should check the diff of the whole branch, right?

But when doing that, we also need to make sure that we ignore any changes from merge commits, like in https://github.com/llvm/llvm-admin/pull/8, otherwise we will essentially end up testing every single subproject as soon as an MR contains a merge commit. IIRC `git diff <base>...HEAD` is the syntax for that, but it's worth testing and looking into.

https://github.com/llvm/llvm-project/pull/82093