Add a fake cc_toolchain_config rule for our fake cc_toolchain to poin…

…t to when Bazel doesn't need C++ toolchain configuration

The toolchain configuration rule we are currently relying on will be removed as part of #8546

RELNOTES: None.
PiperOrigin-RevId: 262952632

tools/cpp/BUILD.empty

@@ -14,7 +14,7 @@
 
 package(default_visibility = ["//visibility:public"])
 
-load("@bazel_tools//tools/cpp:cc_toolchain_config.bzl", "cc_toolchain_config")
+load(":cc_toolchain_config.bzl", "cc_toolchain_config")
 
 cc_library(
     name = "malloc",
@@ -47,8 +47,4 @@ cc_toolchain(
     strip_files = ":empty",
 )
 
-cc_toolchain_config(
-    name = "local_config",
-    cpu = "local",
-    compiler = "compiler",
-)
+cc_toolchain_config(name = "local_config")

tools/cpp/cc_configure.bzl

@@ -91,15 +91,16 @@ def cc_autoconf_impl(repository_ctx, overriden_tools = dict()):
        repository_ctx: repository context
        overriden_tools: dict of tool paths to use instead of autoconfigured tools
     """
-    paths = resolve_labels(repository_ctx, [
-        "@bazel_tools//tools/cpp:cc_toolchain_config.bzl",
-    ])
 
     env = repository_ctx.os.environ
     cpu_value = get_cpu_value(repository_ctx)
     if "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" in env and env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] == "1":
-        repository_ctx.symlink(paths["@bazel_tools//tools/cpp:cc_toolchain_config.bzl"], "cc_toolchain_config.bzl")
-        repository_ctx.symlink(Label("@bazel_tools//tools/cpp:BUILD.empty"), "BUILD")
+        paths = resolve_labels(repository_ctx, [
+            "@bazel_tools//tools/cpp:BUILD.empty",
+            "@bazel_tools//tools/cpp:empty_cc_toolchain_config.bzl",
+        ])
+        repository_ctx.symlink(paths["@bazel_tools//tools/cpp:empty_cc_toolchain_config.bzl"], "cc_toolchain_config.bzl")
+        repository_ctx.symlink(paths("@bazel_tools//tools/cpp:BUILD.empty"), "BUILD")
     elif cpu_value == "freebsd":
         paths = resolve_labels(repository_ctx, [
             "@bazel_tools//tools/cpp:BUILD.static.freebsd",

tools/cpp/empty_cc_toolchain_config.bzl

@@ -0,0 +1,42 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A fake C++ toolchain configuration rule"""
+
+def _impl(ctx):
+    out = ctx.actions.declare_file(ctx.label.name)
+    ctx.actions.write(out, "Fake executable")
+    return [
+        cc_common.create_cc_toolchain_config_info(
+            ctx = ctx,
+            toolchain_identifier = "local_linux",
+            host_system_name = "local",
+            target_system_name = "local",
+            target_cpu = "local",
+            target_libc = "local",
+            compiler = "compiler",
+            abi_version = "local",
+            abi_libc_version = "local",
+        ),
+        DefaultInfo(
+            executable = out,
+        ),
+    ]
+
+cc_toolchain_config = rule(
+    implementation = _impl,
+    attrs = {},
+    provides = [CcToolchainConfigInfo],
+    executable = True,
+)