[Bazel] Provide filegroups for `@rules_pkg`

[chapuni]

Summary

For now, I have created four filegroups.
They are sufficient for the Clang toolchain.

• @llvm-project//clang:pkg-clang
• @llvm-project//clang:pkg-clang-resources
• @llvm-project//lld:pkg-lld
• @llvm-project//llvm:pkg-llvm-ar

They are available for pkg_tar etc.

[GMNGeoffrey]

This looks reasonable, but I'm not familiar with @rules_pkg. Could you add more explanation to the patch description about the goals of this change?

[chapuni]

@GMNGeoffrey Thanks for the comment.

I could add actual tar rules as an example to use files, in utils/bazel/BUILD.bazel or other directory like //pkg outside @llvm-project.
I didn't do since I was afraid if they were less useful to everyone.
Do you think the commit log would satisfy an explanation of this? (I think so since I often use git-blame)

FYI, pkg_files can be used for bootstrapping clang if also toolchain files are supplied.

I would like to ask you. Is the location of pkg_files reasonable? I tried locating them to other places in @llvm-project,

• //: (BUILD.bazel) -- It requires modifying the repository rule for llvm-raw
• //pkg: or //{clang|lld|llvm}: -- Seems the overlay script doesn't accept new directories defined in llvm-project-mirror.

Since I suppose pkg_files rules would not affect wildcard target specifications from command line,
I have taken an option to locate pkg_files into existing BUILD.bazel.
Other options?

utils/bazel/llvm-project-overlay/clang/BUILD.bazel

 # 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
 
 load("@bazel_skylib//rules:expand_template.bzl", "expand_template")
+load(
+    "@rules_pkg//pkg:mappings.bzl",
+    "pkg_attributes",
+    "pkg_filegroup",
+    "pkg_files",
+    "pkg_mklink",
+)
 load("//llvm:tblgen.bzl", "gentbl")
 load("//llvm:binary_alias.bzl", "binary_alias")
 load("//llvm:cc_plugin_library.bzl", "cc_plugin_library")
 
 load(
     "//:vars.bzl",
     "LLVM_VERSION",
     "LLVM_VERSION_MAJOR",
deps = [
         ":basic",
         ":frontend",
         ":index",
         ":lex",
         "//llvm:Option",
         "//llvm:Support",
     ],
 )
+
+# For packaging
+
+CLANG_EXE = "clang-{}".format(LLVM_VERSION_MAJOR)
+
+pkg_files(
+    name="pkg-clang-exe",
+    attributes=pkg_attributes(
+        mode="0755",
+    ),
+    renames={
+        ":clang": CLANG_EXE,
+    },
+    srcs=[
+        ":clang",
+    ],
+)
+
+pkg_mklink(
+    name="pkg-clang-symlink",
+    link_name="clang",
+    target=CLANG_EXE,
+)
+
+pkg_mklink(
+    name="pkg-clangxx-symlink",
+    link_name="clang++",
+    target=CLANG_EXE,
+)
+
+pkg_filegroup(
+    name="pkg-clang",
+    prefix="bin",
+    srcs=[
+        ":pkg-clang-exe",
+        ":pkg-clang-symlink",
+        ":pkg-clangxx-symlink",
+    ],
+)
+
+pkg_files(
+    name="pkg-clang-resources",
+    prefix="lib/clang/{}/include".format(LLVM_VERSION_MAJOR),
+    srcs=[
+        ":builtin_headers_gen",
+    ],
+    strip_prefix="staging/include",
+)

utils/bazel/llvm-project-overlay/lld/BUILD.bazel

 # 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
 
 load("@bazel_skylib//rules:expand_template.bzl", "expand_template")
+load(
+    "@rules_pkg//pkg:mappings.bzl",
+    "pkg_attributes",
+    "pkg_filegroup",
+    "pkg_files",
+    "pkg_mklink",
+)
 load("//llvm:tblgen.bzl", "gentbl")
 
 load(
     "//:vars.bzl",
     "LLVM_VERSION",
 )
 
 package(
outs = [
         "ld64.lld",
         "lld-link",
         "wasm-ld",
     ],
     cmd =
         "target=$$(basename $<); for n in ld.lld ld64.lld lld-link wasm-ld; do ln -sf $$target $(@D)/$$n; done",
     output_to_bindir = 1,
 )
+
+# For packaging
+
+pkg_files(
+    name="pkg-lld-exe",
+    attributes=pkg_attributes(
+        mode="0755",
+    ),
+    srcs=[
+        ":lld",
+    ],
+)
+
+pkg_mklink(
+    name="pkg-ld.lld-symlink",
+    link_name="ld.lld",
+    target="lld",
+)
+
+pkg_filegroup(
+    name="pkg-lld",
+    prefix="bin",
+    srcs=[
+        ":pkg-ld.lld-symlink",
+        ":pkg-lld-exe",
+    ],
+)

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

 # 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
 
 load("@bazel_skylib//rules:common_settings.bzl", "string_flag")
 load("@bazel_skylib//rules:expand_template.bzl", "expand_template")
+load(
+    "@rules_pkg//pkg:mappings.bzl",
+    "pkg_attributes",
+    "pkg_files",
+)
 load(":tblgen.bzl", "gentbl")
 load(":config.bzl", "llvm_config_defines")
 load(":targets.bzl", "llvm_targets")
 load(":enum_targets_gen.bzl", "enum_targets_gen")
 load(":binary_alias.bzl", "binary_alias")
 
 package(
     default_visibility = ["//visibility:public"],
srcs = glob([
         "utils/yaml-bench/*.cpp",
     ]),
     copts = llvm_copts,
     stamp = 0,
     deps = [
         ":Support",
     ],
 )
+
+# For packaging
+
+pkg_files(
+    name="pkg-llvm-ar",
+    attributes=pkg_attributes(
+        mode="0755",
+    ),
+    prefix="bin",
+    srcs=[
+        ":llvm-ar",
+    ],
+)