Automated rollback of commit 0a65893.

*** Reason for rollback ***

Broke Bazel postsubmit: https://buildkite.com/bazel/bazel-bazel/builds/28021#018f9a8b-8711-4f02-af8a-c29a1e7c6255

#22259 (comment)

*** Original change description ***

Add layering_check support for macOS

There were 2 things with the previous implementation that needed to be improved here:

1. Apple Clang has a bug where it doesn't pass module compiler flags to the underlying -cc1 invocation, so we have to manually pass them directly to that invocation with -Xclang
2. The previous search script was too aggressive and slow for macOS. The macOS SDK has tons of files that aren't headers, and tons of symlin...

***

RELNOTES:
PiperOrigin-RevId: 635852793
Change-Id: I03b0831706a555bbcf141742aefa3bf48ed0caf3

src/test/shell/bazel/bazel_layering_check_test.sh

@@ -144,6 +144,11 @@ EOF
 }
 
 function test_bazel_layering_check() {
+  if is_darwin; then
+    echo "This test doesn't run on Darwin. Skipping."
+    return
+  fi
+
   local -r clang_tool=$(which clang)
   if [[ ! -x ${clang_tool:-/usr/bin/clang_tool} ]]; then
     echo "clang not installed. Skipping test."

tools/cpp/generate_system_module_map.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # Copyright 2020 The Bazel Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -17,19 +17,10 @@ set -eu
 
 echo 'module "crosstool" [system] {'
 
-if [[ "$OSTYPE" == darwin* ]]; then
-  for dir in $@; do
-    find "$dir" -type f \( -name "*.h" -o -name "*.def" -o -path "*/c++/*" \) \
-      | LANG=C sort -u | while read -r header; do
-        echo "  textual header \"${header}\""
-      done
+for dir in $@; do
+  find -L "${dir}" -type f 2>/dev/null | LANG=C sort | uniq | while read header; do
+    echo "  textual header \"${header}\""
   done
-else
-  for dir in $@; do
-    find -L "${dir}" -type f 2>/dev/null | LANG=C sort -u | while read -r header; do
-      echo "  textual header \"${header}\""
-    done
-  done
-fi
+done
 
 echo "}"

tools/cpp/unix_cc_configure.bzl

@@ -534,7 +534,7 @@ def configure_unix_toolchain(repository_ctx, cpu_value, overriden_tools):
         ["/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk"],
     )
 
-    generate_modulemap = is_clang
+    generate_modulemap = is_clang and not darwin
     if generate_modulemap:
         repository_ctx.file("module.modulemap", _generate_system_module_map(
             repository_ctx,

tools/cpp/unix_cc_toolchain_config.bzl

@@ -36,7 +36,7 @@ def _target_os_version(ctx):
     xcode_config = ctx.attr._xcode_config[apple_common.XcodeVersionConfig]
     return xcode_config.minimum_os_for_platform_type(platform_type)
 
-def layering_check_features(compiler, is_macos):
+def layering_check_features(compiler):
     if compiler != "clang":
         return []
     return [
@@ -53,10 +53,8 @@ def layering_check_features(compiler, is_macos):
                     ],
                     flag_groups = [
                         flag_group(
-                            # macOS requires -Xclang because of a bug in Apple Clang
-                            flags = (["-Xclang"] if is_macos else []) + [
+                            flags = [
                                 "-fmodule-name=%{module_name}",
-                            ] + (["-Xclang"] if is_macos else []) + [
                                 "-fmodule-map-file=%{module_map_file}",
                             ],
                         ),
@@ -88,7 +86,7 @@ def layering_check_features(compiler, is_macos):
                         ]),
                         flag_group(
                             iterate_over = "dependent_module_map_files",
-                            flags = (["-Xclang"] if is_macos else []) + [
+                            flags = [
                                 "-fmodule-map-file=%{dependent_module_map_files}",
                             ],
                         ),
@@ -1489,7 +1487,7 @@ def _impl(ctx):
             unfiltered_compile_flags_feature,
             treat_warnings_as_errors_feature,
             archive_param_file_feature,
-        ] + layering_check_features(ctx.attr.compiler, is_macos = False)
+        ] + layering_check_features(ctx.attr.compiler)
     else:
         # macOS artifact name patterns differ from the defaults only for dynamic
         # libraries.
@@ -1530,7 +1528,7 @@ def _impl(ctx):
             treat_warnings_as_errors_feature,
             archive_param_file_feature,
             generate_linkmap_feature,
-        ] + layering_check_features(ctx.attr.compiler, is_macos = True)
+        ]
 
     parse_headers_action_configs, parse_headers_features = parse_headers_support(
         parse_headers_tool_path = ctx.attr.tool_paths.get("parse_headers"),