Add 'third_party/abseil_cpp/' from commit '768eb2ca28'

git-subtree-dir: third_party/abseil_cpp
git-subtree-mainline: ffb2ae54be
git-subtree-split: 768eb2ca28

third_party/abseil_cpp/absl/compiler_config_setting.bzl

@@ -0,0 +1,38 @@
+#
+# Copyright 2018 The Abseil Authors.
+#
+# 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
+#
+#      https://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.
+
+"""Creates config_setting that allows selecting based on 'compiler' value."""
+
+def create_llvm_config(name, visibility):
+    # The "do_not_use_tools_cpp_compiler_present" attribute exists to
+    # distinguish between older versions of Bazel that do not support
+    # "@bazel_tools//tools/cpp:compiler" flag_value, and newer ones that do.
+    # In the future, the only way to select on the compiler will be through
+    # flag_values{"@bazel_tools//tools/cpp:compiler"} and the else branch can
+    # be removed.
+    if hasattr(cc_common, "do_not_use_tools_cpp_compiler_present"):
+        native.config_setting(
+            name = name,
+            flag_values = {
+                "@bazel_tools//tools/cpp:compiler": "llvm",
+            },
+            visibility = visibility,
+        )
+    else:
+        native.config_setting(
+            name = name,
+            values = {"compiler": "llvm"},
+            visibility = visibility,
+        )