Export of internal Abseil changes

--
017c3924d21132085bc20c9be0ae469bfbf2c56c by Gennadiy Rozental <rogeeff@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 338723934

--
8b08c23d7b05232e283b1388cee3eb5bebc2d9c4 by Derek Mauro <dmauro@google.com>:

Add script to test GCC floor (the minimum version of GCC we support,
currently the GCC 5 series)

PiperOrigin-RevId: 338708581

--
afa440ac7c843126b4f99b89ebc071dda1d85a4d by Abseil Team <absl-team@google.com>:

Fix typo in documentation of StatusOr::value_or() ('of' -> 'if').

PiperOrigin-RevId: 338690089

--
97d5008865327fc36b942b96de0d0cacfb909df5 by Derek Mauro <dmauro@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 338568224

--
da5e09a7fedb3217329465d9206b7cbc6677176b by Abseil Team <absl-team@google.com>:

Add `absl_btree_prefer_linear_node_search`

Allow keys of `btree_set`, `btree_map`, `btree_multiset`, and `btree_multimap`
to opt-in to linear search (instead of binary search).  Linear search was
used previously for arithmetic types with `key_compare` of `std::greater`
or `std::less`.

For example, this would be useful for key types that wrap an integer
and define their own cheap `operator<()`.

```
 class K {
  public:
   using absl_btree_prefer_linear_node_search = std::true_type;
   ...
  private:
   friend bool operator<(K a, K b) { return a.k_ < b.k_; }
   int k_;
 };

 absl::btree_map<K, V> m;  // Uses linear search
 assert((absl::btree_map<K, V>::testonly_uses_linear_node_search()));
```

PiperOrigin-RevId: 338476553

--
c56ead7ce6b0a5ad32e3a42904c686448a69451e by Gennadiy Rozental <rogeeff@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 338419417
GitOrigin-RevId: 017c3924d21132085bc20c9be0ae469bfbf2c56c
Change-Id: I1199f3ae917280a3ef20ccc6038abbe34d96ec0b

2 files changed, 90 insertions, 0 deletions

diff --git a/ci/linux_docker_containers.sh b/ci/linux_docker_containers.sh
index 752b5729..b96fe890 100644
--- a/ci/linux_docker_containers.sh
+++ b/ci/linux_docker_containers.sh
@@ -18,4 +18,5 @@
 readonly LINUX_ALPINE_CONTAINER="gcr.io/google.com/absl-177019/alpine:20191016"
 readonly LINUX_CLANG_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20201008"
 readonly LINUX_GCC_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20201008"
+readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20201015"
 readonly LINUX_GCC_49_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-4.9:20191018"
diff --git a/ci/linux_gcc-floor_libstdcxx_bazel.sh b/ci/linux_gcc-floor_libstdcxx_bazel.sh
new file mode 100755
index 00000000..224aef81
--- /dev/null
+++ b/ci/linux_gcc-floor_libstdcxx_bazel.sh
@@ -0,0 +1,89 @@
+#!/bin/bash
+#
+# Copyright 2020 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.
+
+# This script that can be invoked to test abseil-cpp in a hermetic environment
+# using a Docker image on Linux. You must have Docker installed to use this
+# script.
+
+set -euox pipefail
+
+if [[ -z ${ABSEIL_ROOT:-} ]]; then
+  ABSEIL_ROOT="$(realpath $(dirname ${0})/..)"
+fi
+
+if [[ -z ${STD:-} ]]; then
+  STD="c++11 c++14"
+fi
+
+if [[ -z ${COMPILATION_MODE:-} ]]; then
+  COMPILATION_MODE="fastbuild opt"
+fi
+
+if [[ -z ${EXCEPTIONS_MODE:-} ]]; then
+  EXCEPTIONS_MODE="-fno-exceptions -fexceptions"
+fi
+
+source "${ABSEIL_ROOT}/ci/linux_docker_containers.sh"
+readonly DOCKER_CONTAINER=${LINUX_GCC_FLOOR_CONTAINER}
+
+# USE_BAZEL_CACHE=1 only works on Kokoro.
+# Without access to the credentials this won't work.
+if [[ ${USE_BAZEL_CACHE:-0} -ne 0 ]]; then
+  DOCKER_EXTRA_ARGS="--volume=${KOKORO_KEYSTORE_DIR}:/keystore:ro ${DOCKER_EXTRA_ARGS:-}"
+  # Bazel doesn't track changes to tools outside of the workspace
+  # (e.g. /usr/bin/gcc), so by appending the docker container to the
+  # remote_http_cache url, we make changes to the container part of
+  # the cache key. Hashing the key is to make it shorter and url-safe.
+  container_key=$(echo ${DOCKER_CONTAINER} | sha256sum | head -c 16)
+  BAZEL_EXTRA_ARGS="--remote_http_cache=https://storage.googleapis.com/absl-bazel-remote-cache/${container_key} --google_credentials=/keystore/73103_absl-bazel-remote-cache ${BAZEL_EXTRA_ARGS:-}"
+fi
+
+# Avoid depending on external sites like GitHub by checking --distdir for
+# external dependencies first.
+# https://docs.bazel.build/versions/master/guide.html#distdir
+if [[ ${KOKORO_GFILE_DIR:-} ]] && [[ -d "${KOKORO_GFILE_DIR}/distdir" ]]; then
+  DOCKER_EXTRA_ARGS="--volume=${KOKORO_GFILE_DIR}/distdir:/distdir:ro ${DOCKER_EXTRA_ARGS:-}"
+  BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
+fi
+
+for std in ${STD}; do
+  for compilation_mode in ${COMPILATION_MODE}; do
+    for exceptions_mode in ${EXCEPTIONS_MODE}; do
+      echo "--------------------------------------------------------------------"
+      time docker run \
+        --volume="${ABSEIL_ROOT}:/abseil-cpp:ro" \
+        --workdir=/abseil-cpp \
+        --cap-add=SYS_PTRACE \
+        --rm \
+        -e CC="/usr/local/bin/gcc" \
+        -e BAZEL_CXXOPTS="-std=${std}" \
+        ${DOCKER_EXTRA_ARGS:-} \
+        ${DOCKER_CONTAINER} \
+        /usr/local/bin/bazel test ... \
+          --compilation_mode="${compilation_mode}" \
+          --copt="${exceptions_mode}" \
+          --copt=-Werror \
+          --define="absl=1" \
+          --keep_going \
+          --show_timestamps \
+          --test_env="GTEST_INSTALL_FAILURE_SIGNAL_HANDLER=1" \
+          --test_env="TZDIR=/abseil-cpp/absl/time/internal/cctz/testdata/zoneinfo" \
+          --test_output=errors \
+          --test_tag_filters=-benchmark \
+          ${BAZEL_EXTRA_ARGS:-}
+    done
+  done
+done