[llvm] [Bazel] Make LLVM and Clang config headers configurable (PR #126729)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,177 @@
+# This file is licensed 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
+
+"""Configurable build attributes for the overlay.
+
+To view the configurable build attributes in this file:
+
+    bazel query 'kind(".*_flag", @llvm-project//config:all)'
+"""
+
+load("@bazel_skylib//lib:selects.bzl", "selects")
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_flag")
+
+# Common config settings mapping to platform triples.
+#
+# See also: //platform:BUILD.bazel.
+#
+# TODO(aaronmondal): Add triples for more useful configurations as per
+#                   `llvm/include/llvm/TargetParser/Triple.h`.
+
+selects.config_setting_group(
+    name = "aarch64-apple-darwin",
+    match_all = [
+        "@platforms//cpu:aarch64",
+        "@platforms//os:macos",
+    ],
+)
+
+selects.config_setting_group(
+    name = "aarch64-unknown-linux-gnu",
+    match_all = [
+        "@platforms//cpu:aarch64",
+        "@platforms//os:linux",
+    ],
+)
+
+selects.config_setting_group(
+    name = "powerpc64le-unknown-linux-gnu",
+    match_all = [
+        "@platforms//cpu:ppc64le",
+        "@platforms//os:linux",
+    ],
+)
+
+selects.config_setting_group(
+    name = "systemz-unknown-linux_gnu",
+    match_all = [
+        "@platforms//cpu:s390x",
+        "@platforms//os:linux",
+    ],
+)
+
+# TODO(aaronmondal): Split this into `x86_64-pc-windows-gnu` and
+#                    `x86_64-pc-windows-msvc`.
+selects.config_setting_group(
+    name = "x86_64-pc-win32",
----------------
MaskRay wrote:

`x86_64-pc-windows` is more common than `x86_64-pc-win32` and can be used here.

https://github.com/llvm/llvm-project/pull/126729