Do not autodetect C++ toolchain when BAZEL_DO_NOT_DETECT_CPP_TOOLCHAI…

…N=1 is present

This is useful e.g. when all C++ builds happen remotely and there's no C++
toolchain installed on the host machine.

Fixes bazelbuild#5133.

RELNOTES: None.
PiperOrigin-RevId: 196798471

tools/cpp/BUILD.empty

@@ -0,0 +1,48 @@
+# Copyright 2018 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.
+
+package(default_visibility = ["//visibility:public"])
+
+cc_library(
+ name = "malloc",
+)
+
+cc_library(
+ name = "stl",
+)
+
+filegroup(
+ name = "empty",
+ srcs = [],
+)
+
+cc_toolchain_suite(
+ name = "toolchain",
+ toolchains = {
+ "local|local": ":local",
+ },
+)
+
+cc_toolchain(
+ name = "local",
+ all_files = ":empty",
+ compiler_files = ":empty",
+ cpu = "local",
+ dwp_files = ":empty",
+ dynamic_runtime_libs = [":empty"],
+ linker_files = ":empty",
+ objcopy_files = ":empty",
+ static_runtime_libs = [":empty"],
+ strip_files = ":empty",
+)

tools/cpp/CROSSTOOL.empty

@@ -0,0 +1,15 @@
+major_version: "local"
+minor_version: ""
+default_target_cpu: "local"
+
+toolchain {
+ abi_version: "local"
+ abi_libc_version: "local"
+ compiler: "local"
+ host_system_name: "local"
+ target_libc: "local"
+ target_cpu: "local"
+ target_system_name: "local"
+ toolchain_identifier: "local"
+}
+

tools/cpp/cc_configure.bzl

@@ -23,7 +23,10 @@ def cc_autoconf_impl(repository_ctx, overriden_tools = dict()):
  Label("@bazel_tools//tools/cpp:dummy_toolchain.bzl"), "dummy_toolchain.bzl")
  env = repository_ctx.os.environ
  cpu_value = get_cpu_value(repository_ctx)
- if cpu_value == "freebsd":
+ if "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN" in env and env["BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN"] == "1":
+ repository_ctx.symlink(Label("@bazel_tools//tools/cpp:CROSSTOOL.empty"), "CROSSTOOL")
+ repository_ctx.symlink(Label("@bazel_tools//tools/cpp:BUILD.empty"), "BUILD")
+ elif cpu_value == "freebsd":
  # This is defaulting to the static crosstool, we should eventually
  # autoconfigure this platform too. Theorically, FreeBSD should be
  # straightforward to add but we cannot run it in a docker container so
@@ -53,6 +56,7 @@ cc_autoconf = repository_rule(
  "BAZEL_TARGET_LIBC",
  "BAZEL_TARGET_SYSTEM",
  "BAZEL_USE_CPP_ONLY_TOOLCHAIN",
+ "BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN",
  "BAZEL_USE_LLVM_NATIVE_COVERAGE",
  "BAZEL_VC",
  "BAZEL_VS",