merge(3p/absl): subtree merge of Abseil up to e19260f

... notably, this includes Abseil's own StatusOr type, which
conflicted with our implementation (that was taken from TensorFlow).

Change-Id: Ie7d6764b64055caaeb8dc7b6b9d066291e6b538f

third_party/abseil_cpp/ci/linux_clang-latest_libcxx_bazel.sh

@@ -42,7 +42,7 @@ readonly DOCKER_CONTAINER=${LINUX_CLANG_LATEST_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 ${DOCKER_EXTRA_ARGS:-}"
+  DOCKER_EXTRA_ARGS="--mount type=bind,source=${KOKORO_KEYSTORE_DIR},target=/keystore,readonly ${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
@@ -55,7 +55,7 @@ fi
 # 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 ${DOCKER_EXTRA_ARGS:-}"
+  DOCKER_EXTRA_ARGS="--mount type=bind,source=${KOKORO_GFILE_DIR}/distdir,target=/distdir,readonly ${DOCKER_EXTRA_ARGS:-}"
   BAZEL_EXTRA_ARGS="--distdir=/distdir ${BAZEL_EXTRA_ARGS:-}"
 fi
 
@@ -64,13 +64,12 @@ for std in ${STD}; do
     for exceptions_mode in ${EXCEPTIONS_MODE}; do
       echo "--------------------------------------------------------------------"
       time docker run \
-        --volume="${ABSEIL_ROOT}:/abseil-cpp-ro:ro" \
+        --mount type=bind,source="${ABSEIL_ROOT}",target=/abseil-cpp-ro,readonly \
         --tmpfs=/abseil-cpp \
         --workdir=/abseil-cpp \
         --cap-add=SYS_PTRACE \
         --rm \
         -e CC="/opt/llvm/clang/bin/clang" \
-        -e BAZEL_COMPILER="llvm" \
         -e BAZEL_CXXOPTS="-std=${std}:-nostdinc++" \
         -e BAZEL_LINKOPTS="-L/opt/llvm/libcxx/lib:-lc++:-lc++abi:-lm:-Wl,-rpath=/opt/llvm/libcxx/lib" \
         -e CPLUS_INCLUDE_PATH="/opt/llvm/libcxx/include/c++/v1" \